Einstein's theory of general relativity opens the door for the study of other possible universes--and weird universes at that. The Book of Universes gives us a stunning tour of these potential universes, introducing us to the brilliant physicists and mathematicians who first revealed these startling possibilities. John D. Barrow then explains the latest insights that physics and astronomy have to offer about our own universe, showing how they lead to the concept of the "multiverse"--the universe of all possible universes.