Memories of and musings on the relationships between women, from novelist Peterson (Duck and Cover, 1991, etc.). Sisters are the focus of this memoir cum study--the author's two biological sisters, Paula and Maria, her extended sisterhood of women friends, and even the nonhuman sisters she finds in a dolphin pod or a herd of elephants. Peterson searches wide and deep within her own past and those of others to fill in her complex picture of sisterhood. These relationships often involve caregiving--Marla and Paula are nurses, whereas the author, the eldest sister, has adopted the role of family nurturer--but they can be hurtful as well. Peterson devotes one chapter to the breakup of a friendship with one of her ""chosen"" sisters, a cruel and arbitrary rift that she still doesn't understand, though several years have passed. Peterson also describes how she and her sisters were abused throughout their childhood by their mother. On the other hand, she is exclusive of men but for the most part nonbelligerent toward them. Her father was largely absentee, while her younger brother, the father of four girls, is comfortable with women and women's bonds. A few of Peterson's stories and characters stand out: Paula's neurosurgery and how her sisters coaxed her back from a coma; the Crones, a group of postmenopausal women who share the secrets of aging and companionship with great good humor and sensitivity; and a raucous slumber party for women well beyond adolescence. Other pieces are less successful, and finding out that Peterson is bisexual two-thirds through the book, one feels at first betrayed, as if the preceding ruminations on sisterhood have become retroactively incestuous. (For more on this topic, see Sister to Sister, edited by Patricia Foster, p. 1467.) But despite this unwonted secrecy and the book's New Age tinge, this is clearly a labor of love that is both thoughtful and touching.