What of our childhood will survive? When Hanya Yanagihara, a singular, formidable new voice in American fiction, was 10 or 11 and living in Texas, she had an interest in drawing portraits. Her father, a doctor from Hawaii, unsentimental about bodies, keen that his daughter should follow her passions with rigour, had a friend who was a pathologist. He persuaded the pathologist to let his daughter accompany her to the morgue, in order to draw from the flesh.

“She would pull out cadavers and open them up for me so I could draw them,” Yanagihara says. “It was really wonderful. She was a very cool lady. They were already neatly cut and she would fold back the flaps. I would have loved to be a scientist. Disease really fascinates me, what an invader can do to the host body from an imperial perspective but also as an infection…”

That is never an abstract process, though, I say to her.

“No,” she says. “But I love discovering how far a body will go to protect itself, at all costs. How hard it fights to live. But then the fact is,” she suggests, “our bodies don’t care about us at all.”

It is hard to imagine anyone reading the 734 pages of Hanya Yanagihara’s novel, A Little Life, without being curious about the life of the writer who created it. The novel, which is both a dislocating meditation on the trauma of child sexual abuse, and a moving tribute to the possibilities and limitations of adult male friendship and love, was widely greeted as a book of landmark honesty – “the most ambitious chronicle of the social and emotional lives of gay men to have emerged for many years” – on publication in America in the spring (though some critics found its graphic descriptions of sexual violence both voyeuristic and too much to bear).

The reviewer in the Los Angeles Times felt herself unqualified to offer a judgment on the book at all beyond the fact that it was the only novel she had read as a grownup that simply “left [her] sobbing”. The sober New Yorker became uncharacteristically breathless in describing it as a book that could “drive you mad, consume you, and take over your life”. In the two or three days and nights I spent reading A Little Life, compelled to follow the story of Jude, a brilliant New York lawyer, and the flashbacks to his profoundly disturbing childhood that lead him to vivid self-harm, it was hard to disagree with either of those judgments.

And in breaks from reading, I found myself Googling for insights into Yanagihara herself, intrigued by confessional snippets she had offered around the time of publication: that she had, variously, based the book on the unsettling atmosphere of a series of photographs and paintings that she had been collecting for 14 years prior to writing it. That some of the more indelible moments of her childhood were those spent in roadside motels, waiting for her mother to return with the shopping. That she wrote the 375,000 words of her book in something of a “fevered” state every night for 18 months on coming home from work; and that she had fought with her editor to keep much of the horror of Jude’s story intact, as he had argued to leave some things unsaid, to give the reader a break.

A day after finishing A Little Life, and still in its claustrophobic world, I met Yanagihara at the Savoy, where she was staying for a weekend in London (her day job for the past several years has been as editor-at-large of Condé Nast’s Traveller magazine; she is now an editor at the New York Times style magazine T). Before we got on to the subject of pathology and drawing we started by talking about the ways in which A Little Life – which begins as a conventional tale of four young men, friends from college, partying and gossiping and trying to make their way in New York, before it evolves into something much darker – had taken over her existence these past three years.

“I knew when I started it would be about 1,000 manuscript pages,” Yanagihara says, with the true novelist’s sense of fate. “I’d had the characters in my head for a long time. I was writing every single night and all weekend and it is not something I necessarily recommend. Though it was an exhilarating experience it was also an alienating one. In the first part of the book, JB [one of the four friends, an artist] is talking about painting and about how it becomes more real than life itself. That process, which I experienced, is absorbing and dangerous. It is probably one I will never have again, and one I never want again.”

A Little Life is Yanagihara’s second novel. The first, The People in the Trees, is unreliably narrated by a distinguished anthropologist who, late in his career, has been accused by one of the young male Pacific Island subjects he has “adopted” of cruelty and abuse. (The book was based on the real-life story of Daniel Gajdusek, disgraced Nobel prize winner and a distant friend of Yanagihara’s family.) It took her a dozen years to write. Having read both books back to back it seems to me that the second offers an overwhelming answer to questions – of cultural relativity and ethics –raised in the first. Her ventriloquised anthropologist presents a consummate, self-justifying abuser’s voice. In A Little Life, she tells a victim’s story. Is that how she conceived it?

“In some ways. I do want to do something very different with each book. One of the writers I most admire is Hilary Mantel, because in the middle of her career she just changed paths entirely and became just a totally different novelist. The language changes. I think this book is linked to the first but approaches it in a completely different way. The first book was much chillier, more remote. And intentionally so. I don’t think it was a book that anyone loved and I didn’t love it either. It was not a book that was meant to inspire love in the way that I think this one is.”

I’m guessing it took the publication of the first book to give her the confidence to show exactly what she was capable of in the second?

“Yes. I think there are a couple of nice things in coming to this relatively late – I’m 40 now. You have another career, something else to say. Your life has been lived in. Both of these books are about ageing to a certain extent, and as you get older you realise that actually a 65-year-old man can sound exactly like a 40-year-old woman, or whatever. The idea that old people feel differently about life is a fiction. As you get older you are not relying on pure imagination which often just means clichés…”

Though it took her a relatively long time to get here, she has, apparently, been preparing for this book just about for ever, by collecting pictures as oblique reference material (see below). The pictures she accumulated are all portraits of one kind or another that range from Diane Arbus grotesques, to photographs by Ryan McGinley of young men losing themselves in sex and drugs. She keeps them all on a Pinterest page, describes them as by “artists who use their medium not just to storytell but to do psychological plunder”. When she sat down to write, she says, those 20 or so images provided not only the tone, but also the narrative progression of the book for her. Does she think all art is an act of voyeurism of one kind or another?

“Photography is always a kind of stealing,” she says. “A theft from the subject. Artists are assaulters in a lot of ways and the viewer is complicit in that assault. In the same way with the book. I hope readers feel a sense of entanglement in these lives; they are bearing witness to them but there is also something quite intrusive about that.”

I remind her of the arguments or discussions she had with her editor at Doubleday, Gerry Howard, who was asking her to tone down somewhat, and to cut the length of the passages that dwelt on Jude’s abuse. She refused, presumably, to heighten that sense of complicity?

“One of the things my editor and I did fight about,” she says, “is the idea of how much a reader can take. To me you get nowhere second guessing how much can a reader stand and how much can she not. What a reader can always tell is when you are holding back for fear of offending them. I wanted there to be something too much about the violence in the book, but I also wanted there to be an exaggeration of everything, an exaggeration of love, of empathy, of pity, of horror. I wanted everything turned up a little too high. I wanted it to feel a little bit vulgar in places. Or to be always walking that line between out and out sentimentality and the boundaries of good taste. I wanted the reader to really press up against that as much as possible and if I tipped into it in a couple of places, well, I couldn’t really stop it.”

In person, Yanagihara is a likably measured presence, relaxed, Manhattan-sharp, self-effacing, quick to find the laugh in things. But her writing attempts a tone that you don’t often hear in novels these days. Though her book begins as a kind of smart twentysomething social novel, reminiscent for example of Mary McCarthy’s The Group, it takes on a much more gothic cast with the drip-feed of revelations about the reasons for Jude’s self-harm. The lack of solace the book offers gives it a 19th-century feel, not just in its melodramatic length, but in the authorial refusal to let the reader disengage. Reading it you feel you are starting the path of a certain familiar journey, only to have the ironies pulled out from under you. Was it her plan to beguile the reader in that way?

She says she thinks the book is a bit of a parable of adulthood, which begins as something full of social possibility and narrows to something increasingly introspective. “In the end you are really left on your own,” she says. “If you look at the friends who come in and out of Jude’s life and how they are not able to really save him – that part is, I think, an accurate reflection of my adult life, and no doubt of a lot of people’s.”

One of the inspirations for this book, she says, was her best friend, Jared Hohlt, the print editor of New York magazine. Hohlt was her first reader, and much of the book’s philosophy grew out of intense conversations the pair continue to have over supper each Friday night. “Jared runs in a large group of friends who have been together since university or before. They work terrifically hard at staying friends. None of them are legally married or have kids, and this book is also meant to be a homage to a different kind of adulthood, one that isn’t often celebrated in fiction, but which is adulthood nonetheless. An adulthood in which there is a primacy of friendship. It exists perhaps particularly in New York, where people have come to erase their past to a degree in a family of like-minded people. The 20th century was all about romance, but that is quite a recent idea. Friendship is perhaps a purer relationship, I think.”

Has she always lived on her own?

“I have. I have never wanted a family. I don’t believe in marriage though I obviously believe it should be legal for everyone who wants to do it. But it is not something I believe in, nor do the characters in my book, nor do any of my friends.”

Viewed in this way, her book becomes an extreme allegory of the ways that friends (in particular Jude’s eventual partner and lover, Willem) can help to remake a life that has been destroyed, and the limits to that effort when the damage goes so deep.

“I really was inspired by certain fairytales,” she says. “There are no mothers in fairytales. There is a sort of out-of-time quality. They put characters through extreme acts of suffering and often the reward is just getting married…”

The depravity of Jude’s childhood begins when he is left at the door of a monastery as a newborn baby. The idea of institutionalised abuse inflicted on lost boys by figures of trust is very much the nightmarish mythology of our times. Was she drawn to the broader story for some of those reasons?

“Not really. I am not that interested in abuse really. But what I am interested in as a writer is the long-term effect it has, particularly in men. I think women grow up almost prepared for it in a way. Boys still don’t and it happens to a great many of them. It takes away their sense of masculinity. And of course they are not equipped or encouraged to talk about it. It causes terrible psychic harm. I look at my friends who have experienced this, and these are people who are therapised and can discuss anything but they cannot go near this.”

Some men have approached Yanagihara having read the book and said “this happened to me”. What does she say?

“All you can say in the moment is that you wish them the best. But there is a strange quality to these types of confessions. You wonder if it is the first time they have spoken that aloud. But I don’t think fiction can stand in for therapy. I think they are still on their own with it.”

That sense of the loneliness of the human condition seems to inform much of Yanagihara’s understanding of her characters’ lives. It is tempting to look for the genesis of it in her own early life. Her parents grew up in Hawaii, though her mother was born in Seoul. I had read somewhere that as a child she was often moving around, unrooted?

“My father moved a lot,” she says. “He was a doctor, and every time he got beguiled by a new place we would pack up and get in the car and move there. I was born in LA, then we moved to Hawaii, then we moved to New York, then we moved to Baltimore, then we moved to California, then we moved to Hawaii, then we moved to Texas then we moved to Hawaii then we moved to California. This was before I was 17.” She laughs a little. “He was restless. He took off a lot.”

That sense of the road stayed with her, it is the landscape of many of the pictures she collects, and it is the backdrop to Jude’s grim story. Does it reference, too, a peculiarly American conceit?

“Yes. Even now as an adult, when I drive past these motels that are such an iconic part of the American landscape and of this book, little pockets of mystery every 50 miles along the highway, I remember as a child coming upon them and just wondering about the lives that were lived in each of those darkened rooms. So much that compels about America is all those stories we never hear, of lives that are on the margins or off the grid.”

She collects some of those stories, feeds them into her work. Before this book came out, she says, she was telling a colleague’s friend about it, and the woman told a haunting story about being up in Muir Woods in northern California a few years earlier. “She and her husband were hiking and they came to this clearing. They met a boy who was 11 or so, and they got talking and he said, ‘Do you want to come back to my house?’ So they did, and he took them to this little shack in the woods and this older man came out and they talked. The woman initially assumed the man was the boy’s father, but she became sure actually this man was his lover. When she got back to the highway she called the cops. Many lives are lived under the radar. A story like Jude’s is improbable but certainly possible.”

She said earlier, I say, that every woman grows up almost prepared for abuse. Was that her experience?

She doesn’t answer directly. “What I will say is that every female I know has had some sort of experience which is not necessarily violence, but an awareness of being made to be a sexual being before you are ready to be a sexual being,” she says. “I think everyone is at least keenly aware of the likelihood of that...”

The antithesis of abuse is presented in the book as friendship. Has she had experience of trying to help people in that kind of state?

“On a far lesser scale to Jude,” she says. “I mean we might all have had that feeling: as a friend, what is my responsibility to save someone who doesn’t want to be saved? Or tell someone to keep living when they don’t want to live?

“The interesting thing about trauma is that it affects people very differently but it always, always extracts a huge cost.”

She tells another story that feels like it also might have been somewhere in the background of A Little Life.

“I had a friend back in the 80s whose mother dumped her at a nunnery and took off, and then some years later returned and said, I want her back. And the nuns gave her back. And her childhood carried on being epically weird and bad. They were living in cardboard boxes in warehouses, all that. She survived. She went to college. She got married. She teaches. But it has taken from her something: she just has a complete inability to take anything seriously. You will tell her you are upset because an acquaintance died or something, and she will either laugh or she will say ‘Oh’, and won’t know what to say. I am interested in what trauma takes from people, certainly.”

Yanagihara has said a few times she may not write anything else, at least on this scale and on this subject. Does she still feel trapped in the life of her book?

“I have not been writing, partly because I don’t feel I have anything urgent to say and I don’t really feel I should start until I do,” she says. “I understand why writers and artists go back to certain projects time and again. They may be done with it, but the project is not done with them. You have created this thing which you love and sort of resent.” She smiles, and repeats a statement that seems common to many of her readers. “I hope the book will move out of me, but at the moment it still has me in its grip.”

A Little Life by Hanya Yanagihara (Picador, £16.99). To order a copy for £12.99, go to bookshop.theguardian.com or call 0330 333 6846. Free UK p&p over £10, online orders only. Phone orders min. p&p of £1.99.

Every picture… Hanya Yanagihara on some of the images that coloured A Little Life

I wanted my character Jude to feel to the reader like a self-taught human: someone who had to study and attempt as a young adult the sensations and feelings — trust, love, anger – that are most effectively learned in childhood. One thing he’s never able to master, however, is a sense of abandon; that feeling many of us are able to realise at some point in our lives (however briefly), that our bodies are our own to inhabit and move and use however we’d wish, that they are things meant for utility, but also for pleasure. Certainly his friends Willem and JB possess this skill, and when I was writing them, I thought often of the work of Ryan McGinley, who captures perfectly the druggy, hazy, utter unselfconsciousness of the young and the beautiful, the way they move as if weightless, the way they never have to think about how their bodies might fail them.

I’ve long admired Geoffrey Chadsey’s paintings and drawings, both for their strangeness and for their charged, sexualised and defiantly unlovely depictions of men. Collectively, his work — portraits of chimeric males, and earlier paintings of groups of young college-age boys, all sexual energy and hilarity and intimations of violence — feels like a tour through maleness itself, from the uneasy expressions of intimacy among the young to the growing shame with their changing bodies.

I sometimes think of America as not so much a collection of states as one long highway punctuated by motels. One of these motels’ distinguishing characteristics is their sameness: their surrounding area is always denuded of trees; they are furtive, somehow, despite how unprotected, how defenceless they seem. Another is their particular sense of sorrow: they are receptacles people pass through from one place to another, and so, architecturally and aesthetically, they’re not meant to inspire affection. Some of my book takes place in these motels, and one of the characters is, in his way, a personification of a motel. I spent a great deal of time in motels as a child, and it was the strange hollowness I felt in them, even as a young girl, that I found in Hido’s images, which I used to remind myself of the atmosphere I was trying to conjure.