Larry Niven's best short stories in one collection. Stories are based on scientific facts and theories, as in "The Theory and Practice of Teleportation", and are often humorous, as in "Man of Steel, Woman of Kleenex," discussing how Superman's sperm would tear apart Lois Lane. Niven has wonderful ability to take scientific fact or theory and exploit the absurd aspects of it, while still presenting a intellectually stimulating story or essay. The title short story is my favorite short or long story ever, exploring the possibility of alternate unverses, in which every choice that could ever have been made, was made all possible ways.