Two mighty rhetorical questions conclude this enormous biography of Deng Xiaoping (1904-97): “Did any other leader in the 20th century do more to improve the lives of so many? Did any other 20th-century leader have such a large and lasting influence on world history?” The answers emerge from this comprehensive, minutely documented book, but not as predictably as Ezra F. Vogel, a Harvard University emeritus professor of social sciences, assumes.