The Moral Animal by Robert Wright. Socrates said "Know yourself". If you have even the slightest interest in complying, you owe it to yourself to study evolutionary psychology. After reading some evo psych, human behavior actually started to make a little bit of sense. No, really! The Moral Animal is one of the better introductions to the topic out there, and combines good science with good philosophy. Probably the most worldview-changing insights per page of any book out there. Godel, Escher, Bach by Douglas Hofstadter. Several thousand scientists and mathematicians plus the Pulitzer Prize committee can't be wrong, or, if they can be, they certainly weren't in raving about this book. One of the better introductions to number theory, music, cognitive science, biology, logic, art, language, and Zen Buddhism out there. Hofstadter's goal is nothing less than to cut through enough paradoxes to explain consciousness itself, and although in my opinion he doesn't quite make it, you have so much fun getting there that you barely notice. As good as the science is, and as lucid as the explanations are, the real gem of this book is the wordplay; no work before or since has ever come close. Even if you're a Ph. D in all those other subjects and have nothing left to learn, get the book anyway just for the wordplay. How We Decide by Jonah Lehrer. A good explanation of, well, how we decide, which manages to touch on some of the most exciting fields in psychology. It's written in a very popular style, and has the same clarity and fascination as Lehrer's excellent blog, The Frontal Cortex. Guns, Germs, and Steel by Jared Diamond. Why did civilization appear in certain places and not others? What was the original difference between the "haves" and "have nots" that led marginal areas like Greece to become centers of great civilization when the natives of seemingly blessed areas like California never got beyond the tribal stage? No one wants to be racist, but many people have trouble giving a satisfying non-racist answer to this question. Jared Diamond not only gives it, but pummels you over the head with convincing evidence, surveys the field of anthropology while he's at it, and teaches you some surprising things about primitive civilization. Well-written and clearly deserving of its best-seller status. History of Western Philosophy by Bertrand Russell. To be honest, after studying it a while I think large swathes of western philosophy are somewhere between misguided and just plain stupid, but it's a decision no one should be forced to make without being intimately aware of the subject matter. You could spend four years getting a bachelor's degree in philosophy, or you could read History, itself written by one of western philosophy's greatest minds. Russell describes every major philosopher's position clearly and faithfully, and he isn't afraid to give his opinion of each. And you shouldn't be afraid to share it, because he's freakin' Bertrand Russell. Histories by Herodotus. Written back before people had decided that a history book has to be boring, or, for that matter, true. Herodotus weaves myth, legend, and the history of the Persian Wars together into a great narrative that bears more resemblance to something out of Lord of the Rings than to the sort of thing you'd find in the Harvard Journal of Historical Studies. Herodotus himself said it best: "Some things do not happen as they should, and many things do not happen at all. The duty of the conscientious historian is to correct these defects." Herodotus is a master correcter, and everything in his Histories happens exactly right. Book Four by Aleister Crowley. This book extracts the tiny core of usefulness from the vast sea of New Age garbage in the bookstores, while still being decidedly Old Age. It describes the essence of religion and mysticism, and some pointers for getting to that essence, while still being down-to-earth enough to appeal to skeptics, atheists, and the orthodox. Don't let the author turn you off; Crowley's writing is a lot different than what most people expect. The Less Wrong Sequences by Eliezer Yudkowsky. Hard to get into, equally hard to get out of. A series of essays on rationality and how to think that will make everything just a little bit clearer.