THE title character of "Barton Fink" is a self-important New York playwright who hears Hollywood's siren call during the 1940s. He heads West in hopes of becoming a brilliant screenwriter who will bring the problems of "the common man" to life on the silver screen - not that he's met many "common men" in his limited experience or would listen to one if he did.Yes, he's as insufferable as he sounds. Watching his story, though, one often commiserates with him, since the people he encounters during his adventure - from sycophantic fans to maniacal studio bosses - are a million times more insufferable. And they're nothing compared with Charlie Meadows, an insurance agent who lives next door to Barton in his moth-eaten hotel. Charlie is either the nicest guy in the world or the most dangerous and demented. Barton can't tell which is closer to the truth, and neither can we until the story reaches its all-stops-out climax. It should be against the law to reveal more than this about "Barton Fink," which packs more surprises than any American film in recent memory - in its story, its characters, and its visual style, which ranges from Hollywood satire and 1940s nostalgia to murder-mystery suspense and a final eruption of full-fledged surrealism. Lending further depth is the movie's recognition of a deep-rooted paranoia in the American mood during the World War II era, and of such accompanying evils as anti-Semitism and random violence, which still cast abhorrent spells today. Credit for the success of "Barton Fink" goes not only to filmmakers Joel and Ethan Coen, but also to the excellent cast they have assembled - led by John Turturro, one of the most gifted performers around, and John Goodman, whose past achievements only hint at the intensity he achieves here. Others include Judy Davis as Barton's could-be girlfriend and Steve Buscemi as a quirky hotel clerk. The movie has flaws: A subplot involving a famous novelist (clearly based on William Faulkner) is overlong and repetitious, and a few of the picture's stylistic ideas owe a too-obvious debt to David Lynch's dreamlike devices. (Alert spectators may also observe nods to Clifford Odets and Orson Welles, among others.) Yet most of the picture is as original as it is startling, as courageous as it is outrageous. "Barton Fink" marks a major step forward in the Coen brothers' career.