An encyclopedic yet personal and imaginative account of human genetics by someone who has ``ridden briefly over the ground'' he wishes to cover. Shapiro (Chemistry/NYU) divides his discussion into ``Yesterday,'' ``Today,'' ``Tomorrow,'' and ``After Tomorrow,'' providing historical chronology as well as future speculations. ``Yesterday'' begins with Mendel and moves on to Morgan and the fruit-fly group at Columbia at the turn of the century, revisits the Eagle Pub in Cambridge in 1953 (site of notable Watson-Crick conversations), and moves apace to the mid-70's and the birth of biotechnology with the work of Walter Gilbert at Harvard and Fred Sanger at Cambridge. ``Today'' begins with the launching of the project to map and sequence the entire human genome: the promises, the problems, and the politics. Shapiro chooses the metaphor of DNA as literary script to be decoded and describes genetic diseases as various typos and misreadings. He spends considerable time explaining techniques in current use, such as DNA fingerprinting and chromosome walking. This is tough stuff, but Shapiro does well by his language analogies. And the two sections on the future reveal that he is no novice at speculation. Indeed, he raises the specter of people gaining intimate knowledge of one's personal genome by obtaining a hair or other easily shed body sample--for all the world a 21st-century analogue of black magic, in this case enabling the future ``magician'' to know just what ills one is heir to. Shapiro concludes with the optimistic view that humans may someday dip into the germline to create subspecies with different traits. That, plus interesting asides on the English royal family, Jefferson's descendants, the origins of the Jewish ``race,'' and other examples of DNA sleuthing, add spice and potential controversy to a first-rate study.