The fourth novel by the still-young Sommer (Nearing's Grace, Lifetime, Last Resort) takes place putatively in New York City in the three days before New Year's, but in fact most of the action is in eponymous Jack Haz. zard's head. Hazzard, a 30-year-old fiction writer successful enough to give a reading at The New School, has internal voices, 13 of them, talking, adominishing, cajoling, carping constantly. There's the Mother, Father, Teacher, Boy, Actor, Writer, Paranoid, Recluse, Punk, Depressive, etc. With this, Sommer introduces a new concept of the self to fiction: it's like an overcrowded car full of back-seat drivers; before you get anywhere, everybody has to have their say. The book is, well, slow moving. Sommer's point, it seems, is that we're all a mass of conflicting roles searching for coherence. This makes the book ""psychological,"" and one could criticize the psychology for being textbook-level sophomoric if Sommer hadn't beaten one to the punch: he interrupts his narrative to give long, undigested quotations from elementary psychology textbooks, perhaps in the hope the reader will infer that his characters have depth and meaning. They don't. Marcelline, the awesomely stereotyped 37-year-old Italian divorcâ€še, is alive only as a force capriciously demanding kinky, abusive sex. Hazzard's parents--the cause of Hazzard's split-personalities--appear mostly in flashback. The one thing we know about them is that they're sexually immature. Hazzard's mother does stripteases before her young boy, his father sets Hazzard up with prostitutes. Hazzard himself, split into the Tower of Babel, never comes into focus. His strong suit is ambivalence: trying to be many people at once, he's hardly anyone at all. As for plot, it's mostly Hazzard seesawing back and forth over what to do about the teasing Marcelline. For plot excitement, he rapes her and almost defenestrates her, but even this scene is unconvincing. Although the book has a few moments of humor and cleverness, the gimmick of the babbling voices constitutes a fictional premise that would have been better off left to a quiet life in the author's head.