Robert Shiller, Nobel Prize-winning economist and creator of the widely followed CAPE (Cyclically Adjusted Price-to-Earnings) ratio, published the first edition of this book in March 2000, days before the NASDAQ peaked and began its 78% decline. In it, Shiller argued with quantitative rigor that U.S. equity markets were dramatically overvalued by any historically grounded metric and that the cultural narrative of a permanently elevated new economic era was a textbook manifestation of speculative bubble psychology. The book draws on behavioral economics, historical market data, and social psychology to explain how bubbles form: amplifying feedback mechanisms, new era narratives that justify abandoning historical valuation norms, reduced tolerance for dissent, and institutional incentives that push financial professionals to validate rather than challenge prevailing optimism. The second edition, published in 2005, warned of a parallel bubble in housing, and the third, published in 2015, identified potential overvaluation in bonds. Throughout, Shiller maintains the unusual combination of rigorous quantitative analysis and genuine intellectual humility about timing — he never claims to know when the correction will come, only that current prices embed assumptions about the future that history does not support.