A moving study of the dynamics of sibling relationships. Sandmaier's latest (The Invisible Alcoholics, 1980, etc.) should help revise our understanding of the role siblings play in personal development, as the author points out that siblings can be as important as parents in determining everything from future relationships to physical health and even longevity. The study she offers here of both the technical and general literature on sibling relationships is humanized by interviews with hundreds of people about their relations with their brothers and sisters. Sandmaier investigates the often overlooked meanings that gender holds for brothers and sisters; includes interesting evidence of the effect of ethnicity and nationality on sibling relationships (WASPS are much less comfortable around their siblings than are African-Americans); and provides well-chosen examples, from literature and literary lives, of the complexities and wonders of sibling relationships. Theoretically minded readers will appreciate the author's emphasis on the constructedness of such relationships, and the consequent possibility that -- rather than being innate or predetermined -- they can be changed. There are quibbles -- Sandmaier fails, for example, in her claim for the consistency of findings in birth order studies -- but her analysis for the most part is striking and even inspired. Necessarily, this is a study also about parents -- both abusive ones and successful -- and prospective parents will benefit from it. It closes with encouraging but not treacly advice for those interested in improving relationships with siblings. In its eloquence, evenhandedness, and common sense, a book that rises heads and shoulders above the general run of pop-psych material.