INTERVIEWS with Joel and Ethan Coen often start by announcing how rarely the Coen brothers give interviews.It's true these maverick filmmakers don't exactly burn up the media with eagerness to promote themselves or their work. But they're not loners, either, cultivating an anti-Hollywood mystique the way some outsiders do. From all evidence, they are just dedicated moviemakers who care more about cinema than about hype. And they don't mind occasionally sitting down with a critic to discuss their work, as they've done with me a couple of times, most recently over breakfast in a Manhattan coffee shop. Our chief subject of conversation was "Barton Fink," the newest and most brilliant film of the brothers' career. It opened with a gigantic splash at the Cannes Film Festival last May, winning not only the grand prize but also a directing award for Joel Coen and a best-actor award for John Turturro in the title role. Even after this success, however, it is far from clear that "Barton Fink" will be a hit with American moviegoers. In addition to being talented, the Coen brothers are insistent about marching to their own drummer - heeding their own visual and narrative ideas rather than time-tested formulas that make for happy investors and big box-office returns. They carry this tendency to an extreme in "Barton Fink," which promises to make the picture a hard sell for Twentieth Century Fox, the studio that is releasing it tomorrow. Fox also released the previous Coen film, "Miller's Crossing," which sold few tickets last year despite a strong cast and an offbeat story about crime and passion in the gangster world. Their thriller "Blood Simple" and the comedy "Raising Arizona" did well but did not establish them as reliable hitmakers. "Barton Fink" is the most adventurous movie yet from the brothers, who always write their screenplays together and then divide up the production chores, with Joel as director and Ethan as producer. Their new movie "pushes the audience a little" with unexpected twists and turns, admits Joel with a smile. But that's only because the movie's plot is intended to shake up its own main character, a New York playwright who goes to Hollywood in the 1940s with the hope of becoming a screenwriter. "Barton is kind of full of himself," explains Joel, "and smug in his assumptions. It's the ambition of the movie, right from the beginning, to shake his assumptions up. Everything is a sledgehammer on Barton's world." 'I guess it's true we've let the visual element go a little farther than usual here," Ethan adds, acknowledging the film's unusual blend of images and elements. "But it doesn't seem adventurous to me. We recognize it may have a limited audience - it's not going to be 'Back to the Future' or 'Terminator 2,' of course. But what's not to like? It's really fun for us!" When they talk about fun, the Coen brothers have two things in mind: the joy of creating a visual experience that packs real excitement for an audience, and the challenge of developing fully rounded characters. 'It's about the characters, and the way they express themselves," says Ethan, explaining the underlying logic of the picture. Joel agrees. "It became less important in this movie for us to be absolutely faithful or consistent," he says, "than to say something about the characters by creating a visual context that made sense for them.... A certain image seemed important as something to say about the character, even if that image might not be entirely logical or possible...." What's fun for the filmmakers in "Barton Fink" should also be fun for audiences, the Coens continue, even if the experience is different from what Hollywood offers. "If people give themselves over to the movie," Joel insists, "it's not a puzzle to be deciphered, it's not a lot of work." In fact, Joel continues, he and his brother often find supposedly conventional films to be more bizarre than their own imaginings, especially when the makers of those formulaic pictures struggle to fit trendy "high concept" ideas into marketable Hollywood packages. Ethan concurs with this observation, using the Hollywood hit "Pretty Woman" as an example. "We were trying to figure out how they came up with that story," he says with a laugh, "about a businessman who goes to L.A. and hires a prostitute to attend important business functions with him for a week. We could never do that. People would accuse us of being off the wall!"