A retired book critic, recently widowed and convalescing after a crippling car accident, lies in bed, compulsively making up stories. Sound familiar? Perhaps it reminds you of a novelist, recovering from a near-fatal illness, who scribbles away in his red notebook like a man possessed (Oracle Night). Or a former insurance salesman who, lung cancer in remission, undertakes a written record of the errors of humanity (The Brooklyn Follies). Or an academic grieving the death of his family who becomes obsessed with writing a book about a forgotten silent film comedian (The Book of Illusions).

A generous reader would argue that Paul Auster has seized on his essential themes (narrative, words, chance, death), and, like his hero Samuel Beckett, is repeatedly recasting them in ever-more economical and powerful ways. A fed-up reader would reply that Auster is a lazy old chancer writing the same book over and over again.

At the opening of his eleventh novel, Man in the Dark, everything is in place for the sort of cool, allusive, metaphysical mystery that Auster is famous for. But then it changes tack, and becomes something altogether more plain and direct.

August Brill, the 72-year-old narrator, lies in the dead of night, thinking - about his late wife, Sonia, and his daughter and granddaughter, who have both lost partners (Miriam's husband has left her, and Katya's boyfriend Titus was killed). When thinking becomes too hard, he tells himself stories: “They might not add up to much, but as long as I'm inside them, they prevent me from thinking about the things I would prefer to forget.”

This night's story is about Owen Brick, a man who wakes up, perplexed, wearing a military uniform, in an unfamiliar landscape. It turns out that he's in an alternative reality: an America in which the 2000 election led to states seceding from the federation in protest; in which the World Trade Centre still stands and Iraq is un-invaded, but civil war rages. There are, Brick learns, many worlds, each “dreamed or imagined or written by someone in another world”; the civil war has been imagined by an old man, and to end it Brick must kill him. That man is August Brill.

This is exactly the kind of plot-will-eat-itself meta-fiction that Auster has been weaving for more than 20 years, but it seems churlish to complain when he handles it so expertly: we are swept along with Brick through the mirror-world in a dreamlike, powerless state. Until Brill loses interest, that is, and Brick suddenly dies.

In another Auster novel, the Owen Brick narrative might have easily migrated across the border from fantasy into reality, but here it is sharply cut off: postmodern tricks are ditched in favour of memory and emotion as Brill's made-up story is replaced by his real-life story, beginning with his romance with Sonia in the Fifties, and ending with the truth about Titus's murder, “the disaster I've been struggling to avoid all night”.

It's a bold move, but not a hugely successful one: Titus's death feels like it should be shocking, but we care more about the unreal Brick than we do Katya's hastily sketched boyfriend. And while Brill's scattered ruminations on conflict - the Second World War, the Iraq war, his imaginary civil war - reveal its insidious, inescapable power, his bleak Beckettian mood seems forced: “Peace on earth, good will toward men. Piss on earth, good will toward none. This is the heart of it, the black centre of the dead of night ...” (His sour conclusion to the story about Brick is a similarly half-baked Beckettism: “Life goes on ... and then it stops”.)

In fact, Brill never comes fully to life, and as he broods on into morning, you are left yearning for some good old artful Auster plotting: the sort that keeps the pages flicking tightly over rather than drifting to an unsteady close.

Man in the Dark by Paul Auster
Faber, £14.99; 180pp Buy the book

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