From the very cover of M2M's second album, The Big Room, it's clear that our little girls have matured.

On their first album, they were just girls -- they looked like young girls on the cover and they made music that was sweet and innocent, the sound of pre-teens making polished pop.

In an age of tarted-up, sexually-charged teen pop, that kite didn't fly, even if the music on their debut was rather charming.

Still, one of the rules of pop is that it needs to sell, and if it doesn't, a change is gonna come -- something that is crystal clear on The Big Room.

The duo still look young, but they're looking worldly on the cover, with lots of makeup, crimped hair, fairly low-cut tops.

Open it up, and Marit looks like a worldlier Jessica Simpson while Marion, in her tight "Fabulous" tank top, seems like a tamer Eliza Dushku.

Neither are as trampy as Willa Ford, but after the deliberately sweet charms of the debut, the marketing feels nearly as shameless.

Fortunately, the music proves that M2M still has considerable charms -- charms that have even grown, actually.

This isn't as girly as the first album but, contrary to the photos, this is hardly sex-centric teen pop either.

Actually, it sounds like the work of Jewel's accomplished younger sisters, girls that can sing and write melodies, given producers and backing bands that can turn it into rather irresistible mainstream pop.

But there's a problem with that statement: it gives the impression that Marion and Marit are simply the puppets of their producers, pretty faces selling ready-made songs, and that's not really the case.

Marion Raven has a writing credit on every song here, writing three herself; Marit Larsen has no less than eight credits here.

Unlike the teen popsters most critics defame for not writing their own songs (a debatable criteria for artistic merit in any case), M2M write their own songs, and they write well.

No, they don't push boundaries and sometimes their lyrics betray their age, but as crafted songs, they're as winning and melodic as Jewel's best work, and this is a more consistent album than anything she's done outside of This Way.

It's a lush, sweet, engaging album, one that works as well upon close listening as it does as background music -- which is what mainstream, adult-oriented pop should do.

If M2M needs to play up their good looks to sell an album this pleasing, so be it.

This is an album that deserves to find its audience, even through tactics as blatant as that.