I've finally done it. A year after first being ordered to do so by a succession of damp-eyed friends, I've finally finished One Day, the bestselling Hampstead duvet novel that has now been made into a slushy Hollywood blockbuster.

I originally put the book down because the two central characters, who meet on the last day of university in 1988, are both so eminently slappable that I didn't care what happened to them over the next 20 years. Emma's "bluestocking" cleverness does not stop her falling in love with a dim, arrogant borderline alcoholic in the way one might fall into, say, an enormous plothole. And Dexter is the sort of good-looking, overprivileged tosspot whom one could well imagine being made "decent", over the course of 20 torturous years of late-night phone calls and missed connections, by the love and loss of one good woman; but a faster, simpler alternative might have been to hold his head down a toilet till the kicking stopped.

Nonetheless, Dexter and Emma are each other's One True Love, and the pursuit of One True Love, as we are doggedly informed by almost every film, book, pop song and cereal packet that deals with adult emotional interaction, can never be thwarted or questioned. So, they marry, move in together and open a little artisan deli that sells "jars of duck confit", and so overwhelming is the weight of expectation that one of them just has to die in a tragic bicycle accident. The savage predictability of this ending, which I could not bring myself to dignify with a spoiler warning, bears out the tendency of the One True Love philosophy to disintegrate in the face of real life, which has an annoying tendency to carry on after the book is closed and the cameras stop rolling.

The relatively recent cultural narrative of The One - the idea that everyone has a soulmate whom they are destined to love for ever, and that your life will always be incomplete if you fail to meet, mate and move in with that person - is not only implausible, but also cruel. It implies that those who do not find their One will somehow never be complete, that those who divorce, who live and raise children alone, or who find alternative arrangements for happiness, have somehow failed as human beings. To my mind, that's a decidedly unromantic idea.

It's not that I don't believe in true love. I've been in it several times, if only for 30 seconds on the night bus home from Hackney. There are, I am convinced, people out there for whom only the girl they met in Year Ten French or the boy they met in the back of the sticky indie disco will ever do, and no other relationship can possibly compare. I know couples like that, and I'm happy for them.

The three Ms

Those people - and I really feel as if saying this might get me shot with heart-tipped Tasers by the love police - are in the minority. Now that we are not obliged to choose between celibate loneliness and yoking ourselves for ever to a person we may grow to despise, most people's lives contain many important relationships, and sometimes those relationships fade or fizzle out. That may not fit in with the dominant ideology - that monogamous marriage is the only possible healthy way to live, love and distribute welfare benefits - but it's a more accurate map of the human heart, which is not a cartoon symbol, but a complicated tangle of meat and blood.

In One Day, every other person with whom Emma and Dexter interact romantically is drawn as an inadequate no-hoper; in real life, however, human love is not a scarce resource. I don't mean to advocate casual sex, polyamory, housing collectives and late nights drinking bad vodka with bisexual activists as alternatives that necessarily work for everyone, though they've always done so for me. The point is that the three Ms - marriage, mortgage and monogamy - do not work for everyone, either, and there's no reason why they should.

The gap between passionate, everlasting, all-consuming romance and meaningless rutting remains relatively unexplored by the publishing and film industries but, to paraphrase John Lennon, a great many people live in that gap. In real life, while we're all busy chasing The One, there is a superabundance of romance, friendship, partnership, sex and adventure to be had - and that's the most romantic thing of all.