For upper-division courses in thermodynamics or statistical mechanics, Kittel and Kroemer offers a modern approach to thermal physics that is based on the idea that all physical systems can be described in terms of their discrete quantum states, rather than drawing on 19th-century classical mechanics concepts.
This book gives an elementary account of thermal physics. The subject is simple, the methods are powerful and the results have broad applications. Probably no other physical theory is used more widely throughout science and engineering.