What are some good books?

This question may seem very straightforward, but the key to this question is what I mean by “good.” I am not looking for a sad, emotional novel. I am also not looking for a happy, feel-good novel. By “good book,” I mean a book that enlightens the reader, and brings a new understanding of the world and how it works. If there is a book that you think that it is important for everyone to read, then submit it as an answer to this question. If there is a book that has had a profound impact on how you view the world, then submit it as an answer. This question is looking for the books that are the best of the best. The book can be either fiction or non-fiction.