'A magnificent, defining work by the foremost authority on the transition from quantum to classical. Over the past forty years, Zurek has put forward one groundbreaking idea after another about how interactions of quantum systems with their environment explain the many puzzling aspects of the emergence of classical behavior. His guiding principle, 'let quantum be quantum,' has turned out to be the key to unlocking the secrets of how quantum systems effectively become classical. The theories he has developed, from einselection to quantum Darwinism, have led to a seminal shift in our understanding of the quantum-to-classical transition and have been confirmed time and again in the laboratory. Written in an impressively engaging and accessible style, the book is the definitive text on all aspects of the quantum-to-classical transition. It will be an indispensable companion for anyone interested in modern quantum mechanics, from students to researchers.' Maximilian Schlosshauer, University of Portland