The lecture notes of Julian Schwinger's UCLA course consist of three parts corresponding to the three quarters of teaching. The first part begins with an analysis of Stern—Gerlach-type experiments which accomplishes a self-contained physical and mathematical development of the general structure of quantum kinematics. The second part proceeds from there. The response to infinitesimal time displacements yields the equations of motion. Then the Quantum Action Principle (QAP) is derived, and accepted as a fundamental principle. In a sense, the rest of part two and all of part three consist of instructive applications of the QAP.FROM THE REVIEWS: MATHEMATICAL REVIEWS "The book is packed with exercises for the reader to attempt...Anyone who works religiously through these exercises will require a thoroughly adequate command of quantum mechanics." CHOICE MAGAZINE "Editor Englert has performed a service for physicists everywhere by making available this book, which is based on Schwinger's unpublished UCLA lecture notes...There are excellent problems at the end of each chapter...This book would make an outstanding supplement and reference for a graduate quantum mechanics course. Theoretical physicists will delight in this wonderful book, which should be available in the library system of any institution with a research or graduate program in physics. Graduate students through professionals."