A writer's century

William Boyd's last book was the cheekiest literary prank in years. Nat Tate: An American Artist, 1928-1960 was launched on 1 April 1998 at a celeb-studded Manhattan loft party and lauded as a long-overdue study of a brilliant but forgotten contemporary of Picasso, a depressive, alcoholic orphan who had a torrid affair with Peggy Guggenheim before throwing himself off the Staten Island ferry. But it turned out to be an intricate hoax, illustrated by blurred photos of unknowns, smudgy abstracts by Boyd and a forged tribute poem by beat poet Frank O'Hara. The art world (especially those who somehow remembered meeting Tate) blushed, and sales of the book stagnated.

A footnote to Boyd's " biography" of Tate appears in his latest work, the memoirs of Logan Mountstuart (1906-1991), writer, womaniser and very definitely fictional. While Nat Tate was a victim of its own tricksiness - over-polished, over-publicised and too clever by half - Any Human Heart thrives on it. It's a sly, hefty and immensely entertaining gallop through school, university, two world wars, a couple of civil wars (Spanish and Nigerian), espionage, imprisonment and the New York art scene of the Fifties (hence the reference to Tate). En route Logan bumps into, among others, Joyce, Hemingway, Woolf, Pollock, Picasso, Waugh, Ian Fleming and the Duke and Duchess of Windsor, most of whom make a very bad impression - Virginia Woolf is a prickly racist, Ian Fleming a porn addict, and Evelyn Waugh might just be the mysterious blond who tried to grope Logan at Oxford.

These apocryphal anecdotes may tickle people in the know, but Any Human Heart remains resolutely unpretentious. This is partly thanks to the distance Boyd keeps from the unfettered arrogance of his protagonist - "I was going to have my book published and these stupid people sat around me ignorant of the fact: they could stew in their Philistine juices for millennia as far as I was concerned," Logan cackles early on. He's clearly related to the vain, vulnerable underdogs that people Boyd's more conventional novels. His terrific powers of storytelling are given free rein here: this is a biography where, for once, you don't know the ending, and he keeps you glued and guessing over many decades.

It's only during Logan's twilight years that his story sags. He ages with amazing haste - suddenly he's ancient, infirm and almost parodically poverty-stricken. Dog food is a favourite meal, as are tins of soup, which, "well diluted, can be eked out to four or five servings". When he begins ferrying dynamite for the Baader-Meinhof Gang, events start seeming a shade farfetched. Perhaps Boyd lacks the same empathy for old age that he could muster for what's gone before, and maybe it's harder to create colourful episodes when there are fewer famous dead people who can be cheerfully libelled to choose from.

But Boyd's chief problem is that he's just too convincing. Halfway through, Logan suffers a tragedy from which he, and the book, can never fully recover. It's involving and occasionally upsetting enough to fool you against your better judgment - at one point I almost found myself thumbing through in search of the photos. Boyd may have pulled off a playful literary sleight of hand, but Any Human Heart none the less stands up as one of his most enjoyable novels to date: generous, witty and sneakily profound.