"The Theory of Operators" is an outstanding work written by Russian mathematician and scientist Vladimir Alexandrovich Sadovnichy. This book is a deep dive into the world of functional analysis and operator theory, which makes it an indispensable tool for students, graduate students and anyone interested in modern mathematical concepts. The book covers a wide range of topics related to operators in Hilbert and Banach spaces. Gardening masterfully explains complex ideas, making them accessible to understanding. He not only expounds the theory, but also illustrates it with examples from real life and related fields of science, such as physics and engineering. This allows the reader to see the practical application of theoretical knowledge and to assess the significance of the topics studied. “Operator theory” will be of particular interest to students and teachers of mathematical and physical faculties, as well as researchers working in the field of functional analysis. The book will be an excellent addition to the library of those who are fond of mathematics, physics, computer science and engineering sciences. It will find a lot of useful both beginners and experienced professionals who seek to deepen their knowledge and expand the horizons of understanding. The topics raised in the book cover such important aspects as spectral theory, operator equations, and various methods of solving problems related to operators. Gardener is not afraid to delve into complex concepts, which makes his work a real storehouse of knowledge for those who are ready for intellectual challenges. He focuses on the importance of operators in mathematics and their role in solving real problems, which makes the book relevant and in demand. The style of Gardening is distinguished by clarity and logical presentation .. It skillfully combines a rigorous mathematical approach with accessible language, which allows the reader not only to absorb the material, but also to enjoy the learning process. The author is also known for his other works, such as "Introduction to Functional Analysis" and "Mathematical Physics", which also deserve attention and can complement the study of operator theory. Operator Theory will be a valuable resource for anyone who seeks a deep understanding of mathematical foundations. It not only expands knowledge in the field of functional analysis, but also inspires further research and discoveries. Readers interested in topics such as “operators in mathematics”, “functional analysis”, “spectral theory” and “mathematical physics” will find in this book a lot of useful information and new ideas. If you want to deepen your knowledge in the field of operator theory and functional analysis, Vladimir Sadovnichy’s Operator Theory is what you need. This book is not just a textbook, but a real encyclopedia of knowledge that will help you become an expert in one of the most interesting and complex areas of mathematics. Do not miss the chance to discover the world of operators and their amazing properties!