Though she's got an MTV reality show of her own, 19-year-old Ashlee Simpson insists she's nothing like her famous sister. But while she now dyes her tresses brown and postures as a rock & roller (her weathered rasp resembles Courtney Love's), she's every bit as pop as Jessica -- even if she savvily cribs from Avril instead of Mariah. Her Autobiography is packed with insidiously catchy songs, especially the first single, ''Pieces of Me,'' in which she sings the praises of canoodling with a friend. But halfway through the album, the recipe gets repeated and you find yourself yawning despite the hooks. If Simpson really wants to be a rock chick, she shouldn't have made such a formulaic debut. That's what pop stars do.