To their credit, the two Wallaces, father and daughter, have disinterred an extraordinary amount of information on Chang and Eng, the 19th-century Siamese twins, and jointly produced a smoothie Wallace narrative. Born in Siam of poor Chinese parents, The Two were crack duck egg merchants by age ten, a shrewd touring exhibit by age twenty--intelligent, quick-witted, able to joke about their eternal bond. As young men, examined by each big city's notable doctor (a free-publicity ploy), they would cry at the mention of surgical separation; later, married to two North Carolina sisters and fathers to 21 children, they regretted that severance was too risky to attempt, an opinion widely held and eventually confirmed by autopsy. Instead they settled for ""alternate mastery"" and mental block-outs, spending three days at a time in each wife's house, doing rather well as gentlemen farmers and on the occasional tour. Although they acted in tandem, their natures were different enough to give nature-nurture debaters a long conference: Chang was always more irritable and sickly, later a heavy drinker, Eng the more even-tempered and healthier; Chang, already ailing, died first, Eng, healthy but panicky, a few hours later. The authors juggle the freakish aspects of their life and a handful of 19th-century euphemisms (the Hyphenated Brethren, the United Brothers) with relevant and marginal trivia, and tuck in the answers to all sorts of speculations, often flippantly or tastelessly: ""If Eng mounted Sallie, then Chang could not be far behind--indeed, he would be dangling seven or eight inches to one side."" And they tend to inflate their significance: had today's surgical procedures been available at their birth in 1811, ""the brothers would have been two little-known egg merchants in Siam rather than the rare and quixotic caprice of Mother Nature that gave the world six decades of awe and wonder."" In this season of assorted freaks, this is the likeliest to pull in passers-by. Each to his own.