Douglas shows his age. And it suits him down to the ground

Michael Douglas did himself no favours with that V-neck jumper he wore to the disco in Basic Instinct, but in Curtis Hanson's Wonder Boys, he really goes out on a limb. He wears his hair grey and lank, tops it with a woollen cap, squints through brown hornrims, and huddles in a ratty car coat and a pink candlewick dressing gown - sometimes both at once. To add to the indignity, Douglas allows Hanson and cinematographer Dante Spinotti to shoot him from hugely unflattering angles, accentuating his sagging jowls and bulldog neck. Catherine Zeta Jones may conceivably have seen him looking this rough, but for the rest of us it's a welcome novelty. Douglas, in his mid-50s, at last gets the chance to be his age and look as though he's seen a few frosty mornings.

Michael Douglas did himself no favours with that V-neck jumper he wore to the disco in Basic Instinct, but in Curtis Hanson's Wonder Boys, he really goes out on a limb. He wears his hair grey and lank, tops it with a woollen cap, squints through brown hornrims, and huddles in a ratty car coat and a pink candlewick dressing gown - sometimes both at once. To add to the indignity, Douglas allows Hanson and cinematographer Dante Spinotti to shoot him from hugely unflattering angles, accentuating his sagging jowls and bulldog neck. Catherine Zeta Jones may conceivably have seen him looking this rough, but for the rest of us it's a welcome novelty. Douglas, in his mid-50s, at last gets the chance to be his age and look as though he's seen a few frosty mornings.

Mornings don't come much frostier than in the Pittsburgh setting of Hanson's literary comedy. It snows, it rains, it snows some more, and then you get your car stolen. This is the kind of town where there is nothing to do but stay in and read - and Wonder Boys is a rare Hollywood film in which people actually do read. And I don't just mean flick through Entertainment Weekly - these characters probably subscribe to The New York Review of Books.

No doubt this unashamedly literary tone contributed to Wonder Boys' poor showing at the American box-office earlier this year. But the film is about to be re-released in the States, having gained a reputation as a minor marvel. "Minor" is the key to its appeal: enormously confident though it is, Wonder Boys refuses all bravura flourishes. Its entertainment value comes from a sort of dogged reluctance to go out of its way to amuse us.

Douglas plays Grady Tripp, a once-prominent author who, in the seven years since his last novel, has lost the plot, in every sense. His problem is not writer's block, quite the opposite. One of his creative-writing students (Katie Holmes, from Dawson's Creek) eventually flicks through his work-in-progress (2,612 pages and counting) and diagnoses the problem as an excess of detail: "the genealogies of everyone's horses, the dental records and so on."

American book culture is fascinated by two diametrically opposed types of writer. One is the Updike sort, the ones who pump out a novel a year: this breed is incarnated here by the ineffable Rip Torn as a best-selling grandee, puffing himself up turkey-like to address a literary conference: "I" (august pause) "am a Writer." The other crowd famously don't deliver for ages, if at all, but skulk enigmatically in the backwaters: committed absentees like Salinger, Pynchon or Harold Brodkey, who for 25 years enjoyed a reputation as the next Proust, then lost it overnight when his novel finally appeared.

If you ever wondered what such scribes do with their lost decades, Wonder Boys offers a demystifying answer. Judging by Grady, they entangle themselves in complex love lives and embark on whimsical road journeys. In a picaresque plot, spun out over a single weekend, Grady tends to his student James (Tobey Maguire), a mercurial, film-obsessed mythomaniac whose short stories map out "his own gloomy gulag". The duo's quest involves a dead dog and an ermine-trimmed jacket once worn by Marilyn Monroe. Screenwriter Steve Kloves (best known for directing The Fabulous Baker Boys) has jettisoned some of the clunkier baggage of Michael Chabon's witty but rambling novel, but allows a number of the book's loose ends to trail tantalisingly.

The film sometimes leans too heavily on near-slapstick, but works best as a generous character opportunity for a personably neurotic cast. Robert Downey Jr may have only one trick these days, that manner of letting mischief flicker over his upper lip, but he does it with characteristic gusto as Grady's trouble-seeking agent. Maguire is a lovely, perplexing mess as the confused wunderkind: you alternately warm to and want to slap this morbid, manipulative book-geek.

Douglas is inspired casting. It would have been tidy and reassuring to hire Jeff Bridges and his amiable shambler act, but Douglas's abrasive gravitas gives body to Grady's doped-out stasis. Even his voice-over, with its acid rasp, is justified simply by his intoning the words "rat's ass". And while we are used to seeing Douglas drape his creaky bones over young things, we can sense from the start that Grady won't get off with Holmes's cerebral ingénue, even if he does fetishise her red cowboy boots. The real sparks are with Grady's academic lover - Frances McDormand, peerless at brittle irony with a sensual undertow.

Director Hanson, who purveyed neon chic in his retro thriller LA Confidential, here switches to a daringly drab palette of brown, dead-leaf yellow and congealed-blood red - an autumnal look for autumnal characters. It suits a film about mid-life crisis, and as an example of that genre, Wonder Boys is far pithier than the glibly self-regarding American Beauty. As a study in suburban blues, it's nearly as good as Ang Lee's wintry, under-rated The Ice Storm.

The wryly heartwarming coda may seem a cop-out, but then these characters have earned their cosy philosophical closure. Like a good comic novel, Wonder Boys imparts its hard-won moral conclusion - that old prodigies must make way for new, that fiction has a terrible way of spilling over into life, and that tormented young whiz-kids should probably get out more. And, most importantly, that even hard-bitten latterday Hemingways must one day ditch that typewriter and invest in a laptop.