WEST PALM BEACH, Fla. - Surely Bobby Darin is less significant than Cole Porter or Ray Charles.

But because of Kevin Spacey's passion for bringing the saloon singer's life to the screen - plus an unconventional approach to telling his story - "Beyond the Sea " is a more compelling movie journey than "De-Lovely " or "Ray," the other two show business biographies this year.

Spacey co-wrote, directed, produced and stars as his professed idol, rolling the dice and steeling himself for most of the praise or the scorn.

Handling Darin's vocals himself, Spacey begins with his signature "Mack the Knife," as if to address right off those who doubt his singing chops.

Minutes later, in a winking exchange, a character charges that Darin is too old to play himself in a movie-within-the-movie.

This is Spacey trying to preempt the inevitable criticism that he, at 45, is too long in the tooth to play a young, eager Walden Robert Cassotto, who would die of heart failure at 37.

While hardly ideally cast, Spacey assumes the character of Darin with such cocky assurance that anyone else in the part becomes unthinkable.

Equally impressive is Spacey's storytelling approach, a non-linear, self-conscious deconstruction of Darin's life that most brings to mind Bob Fosse's stunning autobiography, "All That Jazz."

From the opening sequence, which turns out to be more reel life than real life, through a jumble of cinematic styles, including an enthusiastic embrace of movie musicals of the '50s, with major outbreaks of song and dance in the streets, "Beyond the Sea " is likely to be a love-it-or-hate-it odyssey.

The film is set within a framework that allows the Darin character to tell his story his own way, unencumbered by the facts. Darin narrates, but is occasionally corrected by a 10-year-old version of himself. The device is hardly original, but it does help distance the movie from naturalism, all the better to set us up for its high-stepping production numbers.

The chronological tale begins on the streets of the Bronx - re-created on German sound stages - with young Bobby diagnosed with a rheumatic fever that should have taken his life by the age of 15. But he is taught piano by his doting mother (Brenda Blethyn) and soon climbing the show biz ladder, aided by his brother-in-law agent (Bob Hoskins) and friend-manager (John Goodman). Beaming with pride at his ascent, but feeling unappreciated, is an unabashedly crass Caroline Aaron as Darin's sister.

Rise he does, on the wave of a self-written novelty song called "Splish-Splash," and soon Darin is making movies. Notable among them is "Come September " in Italy, where he meets and woos teen heartthrob Sandra Dee (Kate Bosworth) with the headstrong assurance that he does everything, in a swinging musical montage set to "Beyond the Sea." Bosworth begins all meek and prim, but after marrying Darin and slipping into his shadow, she drifts into a stupor of pills and drink, broken only by a few world-class screamfest fights.

Abruptly, late in his short career, Darin gets politicized by the Vietnam War and converts to folk music, singing peace messages his Las Vegas fans find disconcerting.

Convinced that "people hear what they see," he creates a successful comeback act by adding a gospel choir, an unpersuasive sequence even in this fantasy-laden film.

Still, Spacey manages to carry the day with "Beyond the Sea," even if he never really offers an argument for Darin's significance, why we should care enough to spend two hours with him. It helps if you have first-hand memories of affection for Darin.

For those who know little about the man, though, it is enough to be enthralled by Spacey's gutsy, shoot-the-moon performance and filmmaking.

TITLE: "Beyond the Sea"DIRECTOR: Kevin SpaceyCAST: Kevin Spacey, Kate Bosworth, Brenda Blethyn, Bob Hoskins, John GoodmanRATED: PG-13 (language, sexual situations.GRADE:* * * ½ (on a scale of 5)