There has been hysterical talk, of late, of “no-go areas” in London, districts out of bounds to one community or another. To anyone who moves about the city every day the characterisation is nonsense, an invention of political voices that feed on division. But there is, at the same time, a more private realm in which barriers between communities are being raised: that of storytelling. There is a strain in the culture that wants to put “keep out” signs around the particular experiences of the capital’s varied citizens; to make each community’s tales and histories only theirs to tell.

This is a rare novel, in that hostile landscape policed by cultural studies departments and the 3am stasi on social media, that is temperamentally unafraid of trespass. Andrew O’Hagan goes where his story takes him, deep into the lives of all the communities who live around “the Cally”, the main road that heads north from the capital’s new centre, King’s Cross. The result is a book – it’s hard to resist the word Dickensian – that feels as near an authentic slice of contemporary London life as any packed tube carriage.

He starts, where novels have often started, in the life of that newly endangered species, the white British male academic. Campbell Flynn is an art historian, a writer of bestsellers about the Dutch golden age. Flynn, a tenement Scot who now wears a cravat, has married into that landed caste with “invisible money” after whom the Georgian squares of Islington are named. He and his wife have a townhouse in one of those squares – there’s also a weekend place in Suffolk, where the neighbour stocks “an honesty larder” of local produce at the roadside – but Flynn’s hold on that life is precarious, both materially and psychologically. The novel’s epigraph is from Robert Louis Stevenson: “After a certain distance, every step we take in life we find the ice growing thinner below our feet…” The reader is invited to watch in sympathetic fascination as, over the course of more than 600 pages, Flynn slips below the ice.

He does not go down without a struggle. He’s clever enough to have sensed that cultural survival lies both in serious reinvention and the retention of a sense of humour: “If ambiguity was the spirit of the age, Campbell felt he had been a dutiful officer in that war… He’d marched against Section 28, he’d read every book on the fall of empire, was the proud father of a queer daughter, the first into pronoun therapy, yet his destiny, like everybody’s, was to fall short, and he knew it would be better if he could see the funny side.”

When we meet him, as the capital is giving its head a wobble after the successive concussions of Brexit and lockdown, he is exploring different strategies for that personal renewal. For one thing, he has written, anonymously, a short polemic about the crisis in masculinity, “Why Men Weep in Their Cars”. In his public life, meanwhile, he has befriended one of his students at University College, Milo Mangasha, who has grown up on the estates that rise above Flynn’s own leafy Henry James world; Milo is both an after-hours computer hacker and a radical post-colonial theorist; he is still half-involved with his rap artist mates from school. Flynn wants, naively, to find the common purpose in their worlds; Milo sees an opportunity for show trial and re-education.

This is no simple morality tale, however. In delineating Flynn’s fall, the light of O’Hagan’s attention falls on each of his characters equally – this is a book that comes with a two-page cast list as a preface, to help you keep your bearings. Flynn writes of his beloved Vermeer that he was “the patron saint of individual merit… For thousands of years, privilege and power, determined by birth were the drivers of history. But with this mysterious woman, standing at a musical instrument or reading a letter in the common light of day, we find that it is merit and consciousness, the personal power of ordinary people, that rules the world.” O’Hagan’s book examines what that platitude might actually mean for people like Flynn and employs that “common light” as his own authorial ambition, bringing to full life not only the man of letters, his titled friends and relatives, but the complex day to day of the people who work in the car wash or do shifts at sweatshop garment factories.

Without too much strain, his plotting establishes a web of connection that convincingly takes in all of these worlds: the sitting tenant in Flynn’s Islington basement, Mrs Voyles, bitter remnant of an Islington before gentrification; Cecylia Krupa, praying for a better England in her Polish church; and Zak Byre, the property developer’s son, who divides his time between a £7m flat and direct action for Extinction Rebellion. This being a novel of London, the thread is indebtedness. If you follow the money, O’Hagan suggests, it inevitably leads from eye-watering mortgage to city fixer to money-laundering oligarch to Saudi real estate, with stops for drug dealers and people traffickers and bitcoin investors along the way.

As a journalist, longtime editor-at-large of the London Review of Books, O’Hagan has always been curious to discover the precise tone of new worlds and old. Alongside critical essays on Burns or Stevenson, he has written deeply researched investigations into cryptocurrency and Julian Assange and the dark web; his personal report on the Grenfell Tower fire excited outrage among those who wanted the security of seeing the tragedy only through their own off-the-peg preconceptions, by instead insisting on proper human complication and nuance.

As a novelist, he has tended to write more closely from his own emotional life, from his debut, Our Fathers, set in the Ayrshire housing projects in which he grew up, to Mayflies, 2020’s poignant fictionalised account of a teenage friendship. This book is a departure from that more personal focus, in that he brings into play all of his reporter’s eye for detail and feel for critical ironies. The result is a tragicomedy of manners that has a pitch-perfect grasp of the icy snobberies of Garsington Opera and the patois of drill rappers; a frontline dispatch from the trenches of culture wars and a much-needed, vividly enjoyable broadside to them.

• Caledonian Road by Andrew O’Hagan is published by Faber (£20). To support the Guardian and Observer order your copy at guardianbookshop.com. Delivery charges may apply