One of my enduring interests is the idea of extra-terrestrial life. Aliens. With my deep-seated interest in science-fiction, humanity's steady onward progress and technological development, this is simply a question that comes up often. When writing sci-fi, when reading sci-fi, when pondering the questions of life. Are we alone? If we are, what would that mean? If we are not, what would that mean? Either way, the answer should scare you. This book does a great job of collecting all the reasonable answers to that very question, plus a few more silly ones. A great read for anyone interested in one of the oldest unanswered questions of humanity.