This book presents the essential ideas of coherent states and provides researchers and graduate students with the necessary tools for various applications of generalized coherent state theory. These applications include areas such as quantum information, quantum phase transitions, quantum many-body systems, quantum chaos, and quantum open systems. The aim of the book is to show how coherent states can be applied to an extensive range of physical systems. The authors provide many exercises at the end of each chapter to enhance the mastery of the subject. Throughout the first seven chapters, only an understanding of elementary quantum mechanics is assumed, and for the last six chapters, some basic knowledge of group theory is requested to follow the arguments.