Jack Simons returns to basics and focuses on the foundations of modern theoretical chemistry. He emphasizes the concepts, tools and equations governing the three main theoretical chemistry subdisciplines in this introductorylevel text. An associated website (http://simons.hec.utah.edu/Theorypage/index.html) supplies supplementary material plus many links to other theoretical chemistry sites. The book contains over fifty multipart exercises and worked solutions and provides a concise account of modern theoretical chemistry.