Recent discoveries in cosmology have led to a bizarre new worldview that (to paraphrase Niels Bohr) may be crazy enough to be true. Just consider the litany of mind-boggling new ideas being bandied about lately: the acceleration of cosmic expansion, dark energy (on top of dark matter, yet!), primordial “ripples” in space-time, the quantum creation of the universe from nothing, eternal cosmic inflation, multiple universes . . .Sound crazy enough for you? Fortunately, the new theoretical advances also lead to testable predictions, and we may soon witness the confirmation of some of these predictions by fresh astronomical findings. Alex Vilenkin’s own scientific work has been closely tied to the emergence of the new worldview, from the original ideas to the most recent developments. In Many Worlds in One, he gives an exciting, surprisingly entertaining firsthand account of the birth of the new cosmology, and its fascinating—and at times disturbing—implications.