Graphic, no-nonsense scenarios of human sexual behavior, and evolutionary biology as the framework for interpreting who did what to whom in a given scenario, are the hallmark of this extraordinary work by Univ. of Manchester (England) biologist Baker. His thesis? That humans, no more or less than other animals, are driven by biological forces to ensure their genetic survival. Males need to ensure it is their genes that inseminate; females that they get impregnated by the best genes available. Does that sound like sexual warfare? Game theory? You bet. Baker's credentials are based on lifelong animal research combined with studies of 100 English couples willing to be interviewed and observed in the act. In a nutshell, Baker opines that women are masters at concealing their fertility, men at promoting sperm warfare. The latter relates to evidence that in the face of deposits of sperm from two or more partners in a women's genital tract, there is competition in which one contender's sperm ``blockers'' and ``killers'' try to outdo the other's to succeed in fertilizing the ovum. In 37 fictional scenarios of sexual activity Baker plays out variations on this theme from routine marital sex to homosexuality, group sex, wife-battering, and marital rape, and lifelong monogamy--coming to startling conclusions that infidelity, masturbation, bisexuality, even rape may pay off in the survival- of-the-fittest-genes game. Baker is well aware that he has written a controversial book that will inflame many readers. To his credit, his sexual scenarios are coolly descriptive rather than prurient, as are informative passages on anatomy, the menstrual cycle, and other aspects of physiology. All the same, in reducing complex human behavior to biological urges, he omits emotional motivations and forces. To the question, ``What has love got to do with it?'' Baker would say, ``Not much.'' Expect fireworks and rebuttals, but also serious consideration for the ideas expressed by someone bold enough to open the bedroom door.