Here’s the one thing no one is saying about 8 Mile, the semi-biographical movie starring Eminem that’s confirmed his status as possessor of the zeitgeist: it’s indulgent. Given the opportunity to parlay his star power into a film vehicle, Eminem didn’t seek a project that would expand his public profile or his skill set very much beyond their current boundaries. Instead, he took the rough sketch of his escape from obscurity (but not his rise to fame), changed the lyrics, fudged a few details, and — voilà! — a reluctant star is born. We’ll never know whether equally successful black artists — say, Jay-Z and Puffy — would do the same, because they don’t get to make Hollywood movies, though I’d venture to say they wouldn’t. The pivotal moments in Eminem’s career came when he was trying to convince people he could rap; most black rappers never face such a question.

To hear Em tell it, 8 Mile is his way of keeping it real. The sincerity of the plot is supposed to open a window into the tribulations he suffered before his Slim Shady alter ego carried him to Dr. Dre and MTV. But though he might not realize it, or he might be trying to ignore it, the most honest thing Em could do right now is reveal the sides of himself that he ignores on his albums. Surely he’s not the one-dimensional toublemaker he plays on disc. But for him to offer up anything other than what he’s already become would be to risk everything.

Instead, Em tries to squeeze life out of his fame by investing the battles of his early years with a gladiator-like quality. Rarely are live freestyle battles anywhere near as precise or as sharp as those in 8 Mile, in which Em, as Bunny Rabbit (not kidding), survives a series of, uh, darker MCs, trumping the last one by calling him, of all things, "inauthentic." On the 8 Mile soundtrack, Em raps as Rabbit, and authenticity is foremost on his mind, especially on the title track: "You gotta live it to feel it/You didn’t, you wouldn’t get it/Or see what the big deal is/Why it was and it still is/To be walking this borderline of Detroit city limits/It’s different/It’s a certain significance/A certificate/Of authenticity/You’d never even see/But it’s everything to me/It’s my credibility."

Crossing 8 Mile Road — the border that separates black urban Detroit from the lighter suburbs — gives Em some cred, but it’s really skill he’s after. On "Lose Yourself," he rhymes of his fictional counterpart, "He’s nervous/But on the surface/He looks calm/And ready to drop bombs/But he keeps on forgetting/What he wrote down . . . He opens his mouth/But the words won’t come out." Losing the ability to rhyme is Em’s worst nightmare because the only lifeline Rabbit, or Em himself, has to the world at large is rhyming. And regardless of whether he’s credible or real as a rapper, the fact is that Eminem can rhyme.

The soundtrack to 8 Mile (Interscope) brings him all the way back around, from the desperate, up-and-coming rapper to the talented superstar who can rest on his laurels and then back to the word-hungry rapper whose greatest joy is in the manipulation of rhymes. Check out the extreme assonance of "Love Me," a song on which Em outshines his two new protégés, Obie Trice and 50 Cent: "It ain’t even funny/I ain’t even hungry/It ain’t even money/You can’t pay me enough for you to play me/It’s cockamamie/You just ain’t zany enough to rock with Shady/My noodle is cock-a-doodle/My clock’s cuckoo/I got screws loose/Yeah, the whole kit & caboodle/I’m just brutal/It’s no rumor/I’m numero uno."

Such is the wordplay of an MC with precious little to do save think of words that share vowel sounds and find a way to link them all together. Most rappers in the mainstream don’t concern themselves much with such trifles. It comes naturally to Jay-Z, and it’s the sole interesting thing about Fabolous, but otherwise it’s the preserve of the underground diehard. For all the keepin’-it-real bluster of the 8 Mile soundtrack and the movie itself, that’s where Eminem’s true talents rest. The white kid crossing the racial line, coopting a black art form, and trying to get noticed isn’t looking for superstardom. He just wants to be acknowledged. And for that, he knows he has to be twice as good.