'An excellent text....The postulates of quantum mechanics and the mathematical underpinnings are discussed in a clear, succint manner.'--American Scientist, from a review of the First Edition The author introduces major additions and updates key presentations in the long-awaited new edition of this classic text. New features of the Second Edition include an entirely rewritten mathematical introduction, a discussion of Time-reversal invariance, and extensive coverage of a variety of path integrals and their applications.