Please don't... every time a thread like this shows up on HN, I end up impulsively buying some of the recommended books. I'm usually very happy about the purchase, though. :). Humor aside; not sure if favourite of all times, but definitely impacted my thinking a lot: - "Rationality: From AI to Zombies" - https://intelligence.org/rationality-ai-zombies/ - read this when it was still a bunch of posts by 'Eliezer on LessWrong. It cleaned up my thinking quite a bit, and introduced to couple new ideas from economics, sociology and epistemology. - SICP, obviously. - "How to Win Friends and Influence People", and "How to Stop Worrying and Start Living" - from the father of the whole genre of self-help/personal development, and one whose books are still probably the only good ones in this genre, Dale Carnegie. They explain exactly what it says in their titles.
Also recommended in this reply