This book provides the reader with an explanation of the origin and establishment of quantum mechanics together with a descriptive survey of developments up to the present day. The mathematics is presented in a digestible form yet following the original approach. This second edition presents two new chapters to supplement and extend the first edition material. "Interpretations of Quantum Mechanics" surveys a wide range of current topics, including the multiverse, 't Hooft's ideas for a deterministic local field theory, a summary of the de Broglie-Bohm pilot-wave theory and Anthony Valentini's development of it, and speculative concluding comments on the way ahead.