The book "The Jahn-Teller Effect" offers a comprehensive investigation of the Jahn-Teller effect, which is considered a fundamental concept for structural instabilities and dynamic processes in molecules as well as in the condensed phase. It addresses recent developments in this field, including cooperative phenomena in crystals and the significance of pseudo-Jahn-Teller couplings for symmetry-breaking phenomena in molecular systems. The authors, leading international experts, aim to provide access to this complex topic for both non-expert scientists and professionals looking to expand their knowledge. The book is written in the form of extensive and informative overviews, making it a valuable supplement to existing textbooks. It covers a wide range of topics that are important for understanding Jahn-Teller interactions.