In her debut novel, This American Life contributor O'Neill offers a narrator, Baby, coming of age in Montreal just before her 12th birthday. Her mother is long dead. Her father, Jules, is a junkie who shuttles her from crumbling hotels to rotting apartments, his short-term work or moneymaking schemes always undermined by his rage and paranoia. Baby tries to screen out the bad parts by hanging out at the community center and in other kids' apartments, by focusing on school when she can and by taking mushrooms and the like. (She finds sex mostly painful.) Stints in foster care, family services and juvenile detention ("nostalgia could kill you there") usually end in Jules's return and his increasingly erratic behavior. Baby's intelligence and self-awareness can't protect her from parental and kid-on-kid violence, or from the seductive power of being desired by Alphonse, a charismatic predator, on the one hand, and by Xavier, an idealistic classmate, on the other. When her lives collide, Baby faces choices she is not equipped to make. O'Neill's vivid prose owes a debt to Donna Tartt's The Little Friend ; the plot has a staccato feel that's appropriate but that doesn't coalesce. Baby's precocious introspection, however, feels pitch perfect, and the book's final pages are tear-jerkingly effective. (Oct.)