Although written on an introductory level, this wide-ranging text provides extensive coverage of topics of current interest in equilibrium statistical mechanics. Indeed, certain traditional topics are given somewhat condensed treatment to allow room for a survey of more recent advances. Part I deals with principles of quantum statistical mechanics. Part II examines systems composed of independent molecules or other independent subsystems. Part III considers systems of interacting molecules, and Part IV covers quantum statistics and includes sections on Fermi-Dirac and Bose-Einstein statistics, photon gas, and free-volume theories of quantum liquids.