For this third edition H. D. Zeh has thoroughly revised his book to include important new results. At the same time it retains the features that make it a classic text on irreversibility, and one which clearly distinguishes the latter from time asymmetry. New findings are presented particularly in the chapters on the arrow of time in quantum mechanics and quantum cosmology. Concepts such as decoherence and timelessness are discussed. The book has gained a reputation for its thorough survey of what is known about irreversibility in physics. It investigates physical phenomena in classical, quantum and cosmological settings. Both physicists and philosophers of science who reviewed earlier editions considered this book a magnificent survey, a concise, technically sophisticated, up-to-date discussion of the subject, showing fine sensitivity to some of the crucial philosophical subtleties.