Four hundred years on from the template fashioned by Shakespeare's sorry jesters and tragic clowns, one never expects a modern novelist to be too sanguine over the fate of the stand-up comedian. The trick has been played many times - most recently in Ted Heller's excellent Funnymen (Abacus) - and what emerges is usually only a study in neurosis, personality snuffed out by the greasepaint's scent, fear lurking in the arc-lights' shadow. There is also a gargantuan procedural drawback, in that of all the challenges known to the comic novelist, writing humorously about humour itself is perhaps the most challenging of all. Both these axioms are brought to mind by John O'Farrell's entertaining but in the end slightly laboured novel about the stand-up comic's art.

Or rather the imaginary stand-up comic's art. This is Your Life 's premise is the imposture practised by Adam Fenwick-Symes, the inventive newspaper diarist of Evelyn Waugh's Vile Bodies : the creation of a dense, populous, charisma-strewn world, closely monitored by millions, which exists only in the mind of its creator and whose exposure offers the chance for some decorous satire of the modern media process.

O'Farrell's hero, a nondescript thirtysomething with a long-burnished dream of telling jokes in public, starts the proceedings in lowish water - teaching in a South Coast EFL school, spending his evenings with a fine old collection of pub bores (including his ex-girlfriend Nancy) and glooming over the perpetual absence of the lucky break.

His prospects improve when a local comedy legend, Billy Scrivens, with whom our man has exchanged a fragment or two of small-talk while out running, drops down dead. Interviewed on television, where he is plausibly represented as the deceased's jogging companion, Jimmy suddenly descries a tiny chink in the door of that closely guarded celebrity palisade. After blagging a ticket to the funeral (paid for by Hello! and awash with the rich and famous) he convinces a gullible journalist that he is the latest underground comedy sensation, a performer so principled that he shuns TV and restricts himself to unscheduled appearances at out-of-the-way clubs. A stack of forged reviews from a phantom American tour does the rest. Courtesy of a rave profile in the Sunday Times, his career takes off.

The subsequent rollercoaster ride whisks him all the way from a best new stand-up comedy award (where his acceptance speech loss of nerve - "Look, there's been a terrible mistake" - is taken as a riotous gag) to a dullard contribution to the Today programme and a lucrative ad campaign. Success, inevitably, has its downside: the girls are too keen even for sex-starved Jimmy, and the pub regulars are over-awed by this sudden access of éclat.

What mars This Is Your Life, though, is not the utter predictability of the lessons learned, or even the manner of their learning, but the beetle-browed intentness with which O'Farrell lashes his conceits and comic situations to death. A monologue rant on the catalogue of grudges which Jimmy has hoarded over the years crawls for a page and a half. A promising scene at the comedy awards where Jimmy ends up asking the washroom attendant for change for his tip drags on beyond utility or purpose. Even at 300 large-print pages, the novel has a slightly winded feel, the workaday prose forever straining after effects that don't always come off.

For all that, the conclusion, in which the carpet is pulled from beneath Jimmy's feet and homelier certainties prevail, is ingeniously done. All credit to O'Farrell's resourcefulness, and his relish of the comic twist and detour. At the same time, one can tire of rambling 600-word disquisitions on the kind of food served up at celebrity buffets ("It must take real expertise to create dishes that leave you hungrier than eating nothing" and so on). As the talent scout remarked to his protégé: good material, but delivery needs work.