A fast-paced account for the general reader of the growing body of research into the genes that drive human behavior. Hamer, a molecular geneticist at the National Cancer Institute who previously collaborated with Copeland on The Science of Desire (1994), skillfully synthesizes not only his own discoveries but most of the important findings in the young field of behavior genetics. He shows how genes contribute at the molecular level to such far-flung personality traits and disorders as thrill-seeking, anxiety, sex drive, addiction, and anorexia--and explains how scientists know. The most exciting parts of the book detail the twin studies, personality surveys, and mutant mice experiments through which researchers painstakingly gathered their evidence; even a computerized statistical analysis in quest of a hypothetical gene for neuroticism is suspenseful. As the discoverer of ""the so-called gay gene""--a term he debates--Hamer has first-hand acquaintance with the controversy that often greets claims about the heritability of homosexuality, criminal behavior, and intelligence. He shows good humor and reason in walking through these minefields, debunking some theories (such as those in The Bell Curve) while upholding the right to inquire. The book's awkward introduction misleadingly suggests a pop-psych book, replete with a vignette about a high-school reunion. Although such musings and advice are tendered throughout the book (e.g., how to stay in a relationship with a genetically driven novelty-seeker), they are usually acceptable as the conversational overflow of a scientist whose research has many implications for everyday life. His recurrent theme that ""predisposition is not predestination,"" nicely emphasized in a closing parable about cloning, is welcome. Compulsive reading, reminiscent of Jared Diamond, from a scientist who knows his stuff and communicates it well.