For as long as people have realized that there are other planets out there, there has been speculation about life on other worlds. Writers even as far back as 10th century Japan have talked about extraterrestrials, and we are still talking about the idea today. That kind of staying power deserves some serious recognition. Here are twenty awesome books about aliens of all shapes and sizes! Whether you prefer your aliens friendly in a Star Trek sort of way, or trying to destroy you and your loved ones, you will find something to enjoy in these books.