This unique overview by a prominent CalTech physicist provides a modern, rigorous, and integrated treatment of the key physical principles and techniques related to gases, liquids, solids, and their phase transitions. No other single volume offers such comprehensive coverage of the subject, and the treatment consistently emphasizes areas in which research results are likely to be applicable to other disciples. Starting with a chapter on thermodynamics and statistical mechanics, the text proceeds to in-depth discussions of perfect gases, electrons in metals, Bose condensation, fluid structure, potential energy, Weiss molecular field theory, van der Waals equation, and other pertinent aspects of phase transitions. Many helpful illustrative problems appear at the end of each chapter, and annotated bibliographies offer further guidance.