Mountain Dew-swilling Beemer Minutia, 25, wants to create the ''Beemer brand,'' covering the planet with billboards and soda bottles bearing his image. But when he moves in with girlfriend Paul and takes a job at a California ad agency, he discovers he's just another disposable commodity himself. Like its overly ambitious protagonist, Gaslin's first novel comes undone by its own pretensions. His satirical world of 13-year-old terrorists and castrated boy bands is overly broad, and his characters relate to each other mostly as store-bought objects. ''I just can't put you back in the box, can I?'' Paul tells Beemer. ''The warranty's expired and I'm stuck with you.'' Beemer(TM) is sometimes engrossing but ultimately shallow, like the narcissists it attempts to skewer.