One is tempted to say this book tells you everything you wanted to know about sex but were afraid to ask--except that no one is afraid to ask these days, and we are all but surfeited by the amount of public telling. Indeed, sex scandals aside, the transit from scholarly journal to newsprint is such that hardly any nuance of sexual behavior of beast or human goes unnoticed. So the review that this husband-wife team provides (he is an evolutionary biologist, she a psychiatrist) is less a report on what's new than it is their perspective on the state of sex science today. As such, they are emphatic in stating that just because a behavior is common (e.g., male philandering) does not mean that it is to be condoned: What ``is'' is not to be construed as inevitable or as what ought to be. Having said that, the authors provide a comprehensive summary of the biological, neurological, and developmental differences between males and females, with due regard for the effects of hormones, genes, and culture. Barash provides many examples of animal and anthropological studies relating to courtship, male-male aggression, male violence against another male's offspring, and so on. Lipton draws upon her practice with numerous case studies, such as women who are conflicted or depressed about handling careers and motherhood. Indeed, part of the rationale for the joint authorship was to contrast the styles of the (female) therapist communicating one-on-one with patients with the more distancing perspective of the (male) evolutionary biologist theorizing about bluebirds. Nor are they above using their own marriage to exemplify problems they discuss. Overall, this complementary and not overly technical approach works to their advantage and, along with the temperate point of view, makes this a useful addition to the popular literature. It should be especially good for young people.