The fights resonate still: The Fight of the Century, Down Goes Frazier , The Rumble in the Jungle, The Thrilla in Manila. And the fighters, too--MUHAMMAD ALI, JOE FRAZIER, GEORGE FOREMAN--three complicated and competitive men who happened to be vying for sport's biggest prize when boxing was still a national reassurance and its champion a cultural resource. They fought five times for that title, from 1971 to 1975, ranging across the globe, and their...