Jacqueline Wilson, . . Delacorte, $17.99 (282pp) ISBN 978-0-385-73237-6

Wilson (The Suitcase Kid ; Bad Girls ) again affectingly portrays an adolescent in a remarkably real and wrenching situation. Ten-year-old narrator Dolphin lives with her 13-year-old sister Star and their beautiful, tattoo-covered mother, Marigold, in a Housing Trust flat outside London. Subsisting on welfare, the trio has moved frequently, which has been especially hard on Dolphin (aka "Dol"), who, unlike Star, is plain, wears hand-me-downs and is constantly teased by peers. Marigold, a binge drinker, subjects the girls to dramatic, sometimes frightening mood swings, which render her by turns delusional, agitated and withdrawn. The author deftly balances the pressures placed on Star and Dol, who often wind up caring for their mother and hiding her condition (revealed finally as bipolar disorder) from others, with more universal childhood experiences such as flirting with boys (for Star) and making friends (for Dol). Marigold, still obsessed with her long lost lover Micky, Star's father, successfully searches him out at a concert and brings him home to meet his daughter. When he invites Star to come live with him, Marigold further unravels, culminating in a difficult decision for Dol. The young heroine's candid narrative convincingly and poignantly lays bare her pain and vulnerability as well as her pluck and resilience. And her sense of humor leavens the grim trappings of her situation ("[Micky sent] a little silver dolphin on a silver chain. I wished I didn't always get stuck with dolphins"). Sympathetic and perceptively portrayed supporting players further enrich the novel, including Dol's only friend, Oliver, a wise boy also dealing with a needy mother; the big-hearted foster mother who takes in Dol; and Dol's own newly discovered birth father. Ages 10-up. (Feb.)