The author of the book is one of the leading US experts in the theory and physics of nuclear reactors, known in our country for his fundamental work in this area. The proposed book, designed primarily for students of the relevant specialties of junior courses, is of undoubted interest, since the author managed to mathematically strictly and very physically present an introductory course in nuclear reactor physics. At the same time, a very concise presentation affects almost all the most important modern aspects of reactor physics. In this regard, the proposed book can serve as an excellent introductory course to the famous book by Bell and Glesson "The Theory of Nuclear Reactors. "It is assumed that the reader is familiar with the basics of nuclear physics and such branches of mathematics as differential equations, linear algebra and numerical methods.