Americans have always been the world's most anxiously enthusiastic consumers of "enhancement technologies." Prozac, Viagra, and Botox injections are only the latest manifestations of a familiar pattern: enthusiastic adoption, public hand-wringing, an occasional congressional hearing, and calls for self-reliance. In a brilliant diagnosis of our reactions to self-improvement technologies, Carl Elliott asks questions that illuminate deep currents in the American character: Why do we feel uneasy about these drugs, procedures, and therapies even while we embrace them? Where do we draw the line between self and society? Why do we seek self-realization in ways so heavily influenced by cultural conformity?...