Two-volume course F. Morsa and G. Feshbach holds a special place in the literature on mathematical physics. It is written by physicists for physicists and engineers and shows in action the mathematical methods most successfully used in the study of various fields. The book outlines a number of the most important sections of modern mathematics in terms of their application to the problems of physics and engineering. The great advantage is that the authors everywhere seek to clarify the basic ideas, the essence and the physical meaning of the described methods. Therefore, the book is of considerable interest to mathematicians, to whom it will show new aspects of the methods they know. Some of the methods described (for example, the perturbation theory method in the second volume) are successfully applied by physicists, but are not yet sufficiently known to mathematicians and are waiting for their mathematical justification. Both physicists and mathematicians will find in the book a large number of detailed examples of important applied problems. The course of Morse and Feschbach lies at the intersection of physics and mathematics. It differs from ordinary courses of mathematical physics by its much greater physicality, and from courses of theoretical physics by the fact that it focuses on the development of a mathematical apparatus. The book will be useful to students, graduate students and researchers of mathematical, physical and engineering specialties I generally to all persons facing the application of modern mathematics.