This book is directed mainly at teachers of engineering thermodynamics, but it can also be very useful for the student who wants to read a comprehensive work on the subject alone. The structure of the information contained in the book has been made explicit to the reader, so that he or she can choose what to read and what to leave out with a safe criterion. At the beginning of each chapter, the reader can find one or two types of help. A chapter index can help when forming a global vision of the chapter. We have also considered it useful to insert some comments in the text, generally on conceptual issues that students usually don’t think about at all, but that may be of interest for the teacher, as well as some hints about what kind of things students usually find hard to understand based on our own classroom experiences.