Books: Will the real Mr Theroux please stand up?

Douglas Kennedy is moved by the ruthless honesty of a fictional self portrait

My Other Life by Paul Theroux, Hamish Hamilton, pounds 16

There's a shocking rumour going around these days that Paul Theroux has transformed himself into something of a misanthrope. God knows how such a slight could have attached itself to his good name. After all, the prolific Mr Theroux is well known for his magnanimous Weltaunschauung. Dip into any of his travel books (or his autobiographical fiction) and you will feel an immediate jolt of spiritual uplift as you discover his all-embracing humanity. Just consider, say, his benevolent thoughts on New Zealanders:

"Everyone's wearing old ill-fitting clothes and sensible shoes. They carried string bags...It was the indoor suburban culture of the seaside suburbs of 1950s England, Bexhill-on-the-Pacific, with strangely coloured plates (souvenirs of Cheddar Gorge) on the mantelpiece and plump armchairs..." (The Happy Isles of Oceania).

Having once lived in London for 18 years, he also loathes most things English ("They wallpaper their ceilings"), just as he's also contemptuous of those dreaded journalists who interview him about his work: "But what remains with me is the sorry way they walk, and their plastic briefcases and their fatigue and their shoes - especially their shoes, so trampled and misshapen they have come to resemble a battered pair of human feet." Is it any wonder - given such an acrid temperament - that Theroux has consolidated his reputation as a peevish solipsist with anti-freeze sluicing through his veins, a writer who professes to hate the trappings of literary fame.

Of course, like another celebrated solipsist, Graham Greene, Theroux is also aware of the power of self-mythology. And therefore the image he has fashioned for himself - the fiction he has spun around his writerly persona - is of a wayfaring Greta Garbo with a meat locker where his heart used to be. But (as they say in glossy magazines) is this the real Paul Theroux? Is there a chasm between his fictional effigy and the man himself? Or does the act of writing so blur these frontiers that the novelist eventually invents his own doppelganger - a spectral duplicate of himself which is impossible to shake off. Does Paul Theroux know who Paul Theroux is any more?

This curious conundrum forms the foundation of Theroux's splendid new novel, My Other Life. Like his other quasi-autobiographical stroll down Memory Lane, My Secret History, this alleged fiction is, on one level, a defence of passive spectatorship - that need for detachment and a clandestine inner life without which a writer cannot properly function. But in his new book, Theroux poses the question: does this need for the clandestine other life render you incapable of separating the fictive and the factual? Do you become a character in your own narrative?

Throughout this cunning novel, Theroux invites us to speculate about the dividing line between the veracious and the invented. Upon meeting the Queen, did Theroux actually find himself subjected to a brief blast of royal psychotherapy (when, noting his post-divorce downcast state, Her Majesty counselled: "You will get nowhere if you simply moon around, feeling sorry for yourself")? Was there really an elderly German writer named Andreas Vorlaufer whose career perfectly mirrored Theroux's (and whose short story, Champagne, might just have been based upon the last night Vorlaufer/Theroux spent with his wife before they separated)?

And what are we to make of a writer who undergoes psychotherapy using an alias? Or who, using another assumed name, ends up in the cottage of a fully fledged psychopath (with an alleged penchant for murdering her lovers) who also happens to be a huge Paul Theroux fan?

But the novel's self-aggrandising brio - its identity crisis gamesmanship - is eventually stripped away as Theroux delves into the death of his marriage, his alarming self-pity, his destructive need to keep himself emotionally quarantined.

The self-portrait here is ruthless. He is a man who, having merged with his fictive self, did not attend properly to the very things that gave his life ballast. He finally shows us that he too bleeds.

Arrogance always masks insecurity and doubt. The detached observer always longs for engagement. The aloof sceptic secretly craves the comfort of strangers. Theroux understands these contradictory features of a certain character named Paul Theroux. And towards the end of this ever-intriguing and surprisingly moving novel, he also begins to understand a salient fact of life: we are all the author of our own fiction, but none of us knows the plot.