"Intended for advanced graduate students and active researchers, this textbook deals with some of the latest developments in our attempts to construct a unified theory of the fundamental interactions of nature. Among the topics covered are spontaneous symmetry breaking, grand unified theories, supersymmetry, and supergravity as well as some elementary aspects of string theory and extra-dimension physics. The book starts with a quick review of the basic ideas of quark-lepton physics, gauge theories, spontaneous symmetry breaking, and the standard model, and continues with a discussion of CP violation, left right symmetry, SU(5) and SO(10) grand unification, and the idea of composite quarks and leptons, and the Higgs boson. The last half of the book focuses on the techniques of supersymmetry model building for beginners and presents the minimal supersymmetric extension of the standard model, mechanisms for supersymmetry breaking, and the problems and prospects for supersymmetric grand unification." The third edition has been completely revised and brought up to date, particularly by including discussions of the many experimental developments in recent years.