As you read these words, copies of you are being created. Going way out on the limb, theoretical physicist Sean Carroll explains the Many-Worlds Theory, in which a quantum event causes a world to split off with everything in it the same, except in that other world the event didn't happen. Step-by-step in Carroll's uniquely lucid way, he assesses a century of physics and tackles the major objections to this otherworldly revelation until his case is inescapably established.

"[Carroll] offers us a cogent, clear, and compelling guide to the subject while letting his passion for the scientific questions shine through every page."—NPR