The setting for The Man Who Wasn't There, the latest Coen brothers film, is quiet, clean, sleepy Santa Rosa, California, in the year 1949, where Ed Crane (Billy Bob Thornton), a close-lipped barber, cuts hair, smokes an endless number of cigarettes and, in his idle moments, sits in the barber's chair and wonders how to get out of the rut he is in. His predicament is, perhaps, a metaphor for the experience of watching this film.

When a chatty customer named Creighton Tolliver tells Ed that he has come to Santa Rosa in search of someone who might want to invest in the business of the future - it's called dry-cleaning (hilarious!) - Ed wonders, in the Dick Powell-style voice-over that drives the picture, if this might be the opportunity he's been waiting for. Short of the $10,000 he needs to become Tolliver's sleeping partner, he decides to blackmail Big Dave Brewster (James Gandolfini) for the money. It so happens that Big Dave is having an affair with Ed's wife, Doris (Frances McDormand), and that Big Dave's wife, who owns the local department store where both Dave and Doris work, would divorce Big Dave without a penny if she found out what was going on.

Because this is a Coen brothers film - it's a very typical Coen brothers plot, being a convoluted version of a story that might have been written on the back of a paper napkin by James M Cain - things quickly go wrong, with the blackmail soon compounded by a couple of murders and a trial or two.

Both the title and the setting are an obvious homage to film noir and to Alfred Hitchcock, whose movies Shadow of a Doubt and The Man Who Knew Too Much (a film Hitchcock made twice) are recalled, and then quickly forgotten, as any real comparison with genuine excellence soon becomes redundant. This is not a good film.

Shot on a colour negative, and printed in black and white, this movie has only the patina of film noir; and, to that extent, it's a Maltese Falcon of a film: scrape off the black enamel and there's no gold, just lead. Because while the film may be technically accomplished, this is film noir without the heroes and heroines, the sociopaths, the crooked cops, the expressionist and avant-garde effects, and the witty, hard-boiled poetry of great screenwriters such as Philip Yordan, Ben Hecht and Harry Kleiner. It takes more than a chain- smoking protagonist (Thornton resembles a cheap, waxwork dummy of Humphrey Bogart), a couple of old Buicks and a bit of saturated light to turn a film into something that resembles an American classic. Not so much the stuff that dreams are made of as the elegantly wasteful ideas that fill the minds of advertising men.

Mostly, this is the fault of the script - written by the Coens - which feels arid and desiccated where it tries to be dry, monosyllabic where it affects to be laconic, elliptic where it hopes to sound clipped, and languid where it ought to have been poignant, or pregnant. A shorter film (this runs to 116 minutes) might have helped and, trying to stay awake in some of the slower parts, I formed the distinct impression that the man who wasn't there was the film editor. The movie is not so much The Big Sleep as The Long Nap.

To my mind, the Coens have made only two good films: Blood Simple and Fargo. Everything else they've done has left me as cold as a Minnesota winter. In movies such as The Hudsucker Proxy, Barton Fink, The Big Lebowski and now this latest farrago, the Coens pretend to pay homage to the Hollywood greats; but it's an ironic, dishonest homage, because they mean to denigrate Hollywood, and get a cheap laugh out it, while adding very little that's original of their own to the tradition. Fargo was the exception. But otherwise, theirs are very small jokes writ large. The Coens are all technique and no depth. The Coens are too self-conscious for their own good. The Coens are quirky for the sake of being quirky. The Coens are a con.

It's axiomatic that Coen-heads - the people who get off on "getting it" - will like The Man Who Wasn't There. Coen-heads get off on the mechanics of film-making: the flashy stylistics, the look of the picture, the production design, the score, stuff like that. For them, style is all (the cinematic equivalent of a novel by Ian McEwan) and content nothing. They are the people who walk out of the cinema talking not about the great dialogue, or a great scene, but the great lighting. I know, because as I came out of the cinema where I saw this film, I heard some of them. Just listen to what Frances McDormand herself has to say about being in the movie: "It was the most technically connected I have ever been to hair, make-up, accessories, costume and finding the light. Because the whites of your eyes are the whitest point in the frame, if you blink, it means so much." I rest my case.

The Man Who Wasn't There (15) is on general release from 26 October