Although Chiu uses a catchy title, cute jokes and soft watercolor illustrations by her mother to disguise this book as popular science, she has produced a rigorous and detailed survey of the most recent developments in human genetics; a ""Genetics Primer"" is appended, and many readers will no doubt need it. The first chapter, on a woman who smelled so badly of fish she had to take a three-month leave of absence from work, seems at first the usual, chatty fare of much popular science writing. Within a few paragraphs, however, Chiu has launched into a complex discussion of gene mutation and enzymes. Chiu writes best in her detailed accounts of these genetic oddities, but the names Chiu and others have given the genes responsible (""The Cheeseburger Gene,"" ""The Werewolf Gene,"" ""The Calico Cat Gene"") often belie their seriousness, a problem echoed in Chiu's personal anecdotes, which seem to serve less as relevant commentary than as deliberate bids for a larger readership. Chiu's greater contribution is in her willingness to trust her audience with explanations of genetics research that are long, dense, complicated and surprisingly accessible.