How Could You Do It, Diane?

Stepsisters since they were five, Bethany and Diane were friends as well as siblings, sharing a bedroom when they could have had separate quarters. When Bethany discovers Diane's still form on the basement couch, dead from an overdose of pills, she realizes with a shock just how little she knew of her sister's life. As Bethany's family gropes with their feelings, she looks for solid answers to the ``why'' of beautiful, popular Diane's suicide--answers on which she hopes to base her own future. Like Susan Beth Pfeffer's A Year Without Michael , this book never answers that question, which keeps the emotional bends of the story ringingly honest. Pevsner ( Sister of the Quints ) takes her time with the narrative; she seems ready to explore every angle with readers, in an attempt to make them think through the issues, too. Pat scenes with a therapist do not mar or alter the book's total impact--Bethany handles her problems realistically, and not without grace. Ages 10-14. (Sept.)