Nobel Prize-winning psychologist Daniel Kahneman summarizes decades of research into human judgment and decision-making through the framework of two cognitive systems: System 1, which operates fast, automatically, and emotionally, and System 2, which is slower, more deliberate, and more logical. The book explores the systematic biases that emerge when System 1 overrides System 2 — from overconfidence and anchoring to the planning fallacy and loss aversion — and shows how these biases lead to predictably poor decisions in finance, medicine, policy, and everyday life. For investors, the implications are profound: our intuitive judgments about markets are frequently wrong in patterned, exploitable ways. Kahneman explains why we remember peak and end experiences more vividly than averages, why losses feel roughly twice as powerful as equivalent gains, and why experts are often no better at forecasting than random chance would suggest. Written with remarkable clarity for a book grounded in academic research, it is essential reading for anyone who wants to understand the machinery of human irrationality and make better decisions as a result.