Nobel laureate Kahneman synthesized decades of research into a unified theory of human irrationality: System 1 (fast, intuitive, emotional) and System 2 (slow, deliberate, logical). The most widely cited popular psychology book of the 21st century. Obama, Gates, and countless readers name it as the single book that most changed how they think.

The case for it, the case against, and the rest of the canon open with Pro.