In January, I attended my first ever wedding. Later, I mentioned the event in passing at my publisher’s office. “Wait,” someone said. “You wrote a whole book about a wedding before you’d been to one?”

At that stage I had signed off on the final proofs of my second novel, The Happy Couple. Matrimony structures the plot; the first chapter opens with the couple getting engaged, and we follow them as the ceremony draws near. Why choose this setup when I’d never attended a wedding? Because I thought it would make a good book. To me, marriage is like extreme sports: I’m thrilled for those who partake, and have zero interest in joining them.

Marriage is a nifty narrative device. It brings together people who don’t normally meet, and occasions heaps of conflict. Also, it’s accessible. Everyone knows at least the basics of how their culture gets hitched. We acquire this familiarity as much from art as from life. That’s how I could write a novel about a wedding without ever having been to one. I researched some of the finer points, but I was largely able to rely on the knowledge I’ve absorbed from decades of media immersion, from books and poems, from paintings and song lyrics and movies.

What will become of the marriage plot in art and literature as the actual marriage rate declines? It’s a question we’ve been asking for decades; Jeffrey Eugenides’s 2011 novel The Marriage Plot offers a postmodern spin on the issue. Its heroine, reading English at Brown University, has to choose between two different men while studying virtuoso marriage plotters Jane Austen and George Eliot.

Marriage rates have since plunged even lower. That young people are tying fewer knots has triggered angst in certain quarters, though it’s hardly surprising. It’s hard enough these days for most young couples to rent a flat, never mind spend hundreds of pounds on a cake. But the real conservative bugbear isn’t that fewer people can afford to get married; it’s that fewer people actually want to. That fewer people are entering long-term romantic relationships, or seeking public validation when they do commit. That fewer people are judging themselves against traditional measures of success, or longing for a nuclear family.

For the avoidance of doubt, I’m not suggesting that couples who marry can’t think for themselves. Actually, marriage nowadays is a much more active and informed choice than it was a few decades ago, precisely because it’s no longer the default. Those with personal, specific reasons are still getting married – people like my newlywed friends. But the number of people who marry in order to conform is dropping off.

It follows that the traditional marriage plot will change in art as it has in life. The popular idea is that 19th-century female novelists romanticised marriage – Eliot, the Brontë sisters, and, above all, Austen. A “Jane Austen ending” is supposedly a happily-ever-after. But when we look at post-wedding life in Austen’s novels, the success rate of marriage seems mixed at best. Besides a handful of exceptions (the Westons in Emma, say, or the Crofts in Persuasion), most spouses are either bickering or dead. Yes, we’re generally told in the final chapter that the heroine’s post-nuptial happiness will last – but Austen’s love of irony warns that we shouldn’t necessarily take the narrator’s conclusion at face value.

In 20th-century anglophone literature, the theme of marriage still dominates – but rather than the events leading up to a wedding, we’re more likely to see what happens next. Marital (and extramarital) relations lie at the heart of James Joyce’s Ulysses, DH Lawrence’s Lady Chatterley’s Lover, Virginia Woolf’s Mrs Dalloway and the work of Toni Morrison, a committed Janeite who devoured Austen’s novels throughout her childhood. While not predominately concerned with marriage, Morrison’s novels nevertheless present a similarly nuanced portrayal of the institution. As with Austen, there’s the good (marriage as an exercise of agency between enslaved people in Beloved), the bad (Mavis’s abusive husband in Paradise), and the ugly (literally all the couples in Song of Solomon).

Then there are the groundbreaking portrayals of same-sex relationships, with all their realistic flaws, in the work of authors such as James Baldwin, Djuna Barnes and Jane Bowles. While such depictions still don’t dominate mainstream art, they’ve certainly become more accessible in the 21st century. Brandon Taylor’s second novel, The Late Americans, centres on a gay friendship group where no single character must “represent” their entire community; the tension in Douglas Stuart’s Young Mungo and Shehan Karunatilaka’s The Seven Moons of Maali Almeida comes as much from community strife as from forbidden love between two men.

From the UK publication of Kristen Arnett’s novel With Teeth to Todd Field’s film Tár, starring Cate Blanchett, 2022 was a year of believable, therefore-sometimes-disastrous same-sex marriages. Meanwhile Akwaeke Emezi’s novels and Liv Little’s recent debut Rosewater take the beauty of queer love as their undisputed thematic core.

So where does all this leave the marriage plot? Well, it depends on the author. One can still write a convincing novel with wedlock at the centre: Monica Ali did so excellently in Love Marriage. But this testifies more to Ali’s dramatic talents than to the contemporary importance of marriage. Show a character caring about something, and the audience will care, too – whether it’s a birthday party, a frisbee contest, or a wedding. Novelists will probably always be able to persuade us that marriage is important to their characters. But they’ll have to do the work. They can no longer rely on the reader bringing that assumption to the page.

I did not write my second novel about marriage with a rabid desire to tear the whole thing down. I am not aiming to inspire a wave of divorces, though of course I’ll take it as a compliment if I do. But I did want to approach my fictional wedding with non-judgmental curiosity, tailoring the plot to the characters’ peculiarities rather than forcing a ready-to-wear outcome. I considered what made sense for my protagonists, what they’d want, how they’d behave. Once I’d worked all that out, the rest was just typing.

That’s what I want for real people, too: an awareness of what’s right for them, and the resources to bring it about. Marriage can only benefit from continuing to become less of an obligation and more of a choice. Romance itself need not be a prerequisite for personal fulfilment; we were all, in my view, put on this planet to do whatever the hell we want. The more willing we become in real life to accept unconventional happy endings, the more emboldened novelists will feel to bring them to the page.

• The Happy Couple by Naoise Dolan is published by Weidenfeld & Nicolson.