Allen Klein was like no one the music industry had seen before. The hard-nosed business manager became infamous for allegedly catalyzing the Beatles' breakup and robbing the Rolling Stones, but the truth is both more complex and more fascinating. As the manager of the Stones and then the Beatles—not to mention Sam Cooke, the Who, Donovan, the Kinks, and numerous other performers—he taught young soon-to-be legends how to be businessmen as well as rock stars. In so doing, Klein made millions for his clients and changed music forever. But Klein was as merciless with his clients as he was with anyone else, earning himself an outsize reputation for villainy that has gone unchallenged until now. Through unique, unprecedented access to Klein's archives, veteran music journalist Fred Goodman tells the full story of how the Beatles broke up, how the Stones achieved the greatest commercial success in rock history, and how the music business became what it is today.