Is the multiverse real? Might there be a problem with the Big Bang Theory? And could our physical reality be a mathematical structure? MIT's Max Tegmark has given it all some serious thought, and here he takes an astonishing journey through past, present, and future, and through the physics, astronomy, and mathematics that are the foundation of his work. In this witty, thought-provoking guide, Tegmark not only helps us grasp his often mind-boggling theories, but he also shares with us some of the often surprising triumphs and disappointments that have shaped his life as a scientist.