Janet Jackson posed on the cover of Rolling Stone shirtless, with her then-boyfriend's hands cupping her breasts. Mariah Carey made a video where she cavorted on the beach with a muscular stud. Now, America's sweetheart of the moment stands before us, ready to embrace all the pleasures and challenges of womanhood.

There's just one problem: Britney Spears is still only 19 years old -- and a very young 19 at that, skimpy outfits and slinky videos notwithstanding.

Britney ( * * out of four), her third CD, may be more musically satisfying than previous outings, but as a coming-of-age manifesto, it only emphasizes the teen idol's lack of personality and maturity.

''Say hello to the girl that I am/You're gonna have to see through my perspective,'' she announces on the techno-funk confection Overprotected -- one of several tracks that benefit from the savvy of seasoned Spears hitmaker Max Martin and his colleague Rami. But it's never clear what that perspective is; Spears is too busy trying on pop clichés to find a style of her own.

On the sinuous, Prince-inspired single I'm a Slave 4 U and thumping Boys, the singer is an overzealous but distinctly un-erotic nymphet, huffing and cooing without making any palpable emotional connection to the lyrics. Lonely and Let Me Be -- two catchy, percolating tunes co-written by Rodney Jerkins and Spears herself -- aspire to be strong-woman numbers but end up trite exercises in bubblegum feminism.

Tellingly, the best songs on Britney are the least sophisticated ones. The endearingly earnest ballad I'm Not a Girl, Not Yet a Woman shows Spears at her most winningly tender, while Bombastic Love, another bouncy Martin-Rami collaboration, captures the youthful, un-self-conscious perkiness that made her a star in the first place.

Perhaps, as Spears herself suggests on the former song, all she needs is time. But for now, her modest talents would be better served by more modest ambitions.