James and Katherine are thirtysomething Londoners, both on downwardly mobile trajectories. He's a former dotcom millionaire who now lives in a cramped ex-local authority flat; she's an ex-publisher who works as a hotel receptionist. For a few months in 2006, they have a tentative affair. David Szalay's third novel tells the story of their relationship.

The reason things never get off the ground is that she's just not that into him. At first, it's not clear why (the early chapters are told from James's point of view), and so we share his bemusement  and occasional anger  at her often cold and inconsistent behaviour. Then the perspective shifts to include Katherine as well, and we get an explanation of sorts for her lack of emotional availability.

Szalay captures with unusual accuracy the sheer repetitiveness of a relationship stuck in an early courtship phase. He dwells as much on the couple's preparations for meeting as on the time they actually spend together: the anxious phone calls, the trips to each other's flats. While James masochistically persists, Katherine often gives the impression that it's all too much effort ("I'm tired today." "Why don't you call me tomorrow?"). When feelings are recalcitrant, a relationship can seem like so much bother.

If this were all there was to the novel, it might be a spirit-sapping read. But there are also frequent digressions in which the prose acquires greater richness and energy. Many concern James's business career: his attempt to produce a movie; his moment of dotcom glory. In the present, too, he remains a chancer, and there's a subplot concerning his involvement in a horse-racing scam. These passages have an antic, picaresque feel, and are very funny. They also highlight one of the novel's ironies, which is that real life, for James and Katherine, exists anywhere other than in their dealings with one another.

The work of a sophisticated, quietly original writer, Spring is the antithesis of a romantic comedy  and is all the better for it.