Thinking fast and slow - Daniel Kahneman
There have been many good books on human rationality and irrationality, but this one is masterpiece. That masterpiece is Daniel Kahneman’s Thinking, Fast and Slow. Kahneman, a winner of the Nobel Prize for economics, distils a lifetime of research into an encyclopedic coverage of both the surprising miracles and the equally surprising mistakes of our conscious and unconscious thinking.
This gives insights into various decision making process and thoughts that go into it. It is one of my favourite.