The book "Multigroup approximation in the theory of neutron transfer" by Mark Nikolaevich Nikolaev, B. G. Ryazanova, M. M. Savoskina and A. M. Onions is a fascinating and in-depth study that immerses the reader in the complex but exciting world of neutron physics and their interactions with matter. This publication will be a real find for students, graduate students and specialists in the field of nuclear physics, radiation safety and related disciplines. The book is devoted to multi-group methods that are used to describe the transfer of neutrons in various environments. The authors offer the reader not only theoretical calculations, but also practical examples, which makes the material accessible and understandable. They consider the basic principles and approaches that allow modeling the behavior of neutrons in complex systems, such as nuclear reactors and radiation installations. This makes the book relevant not only for theorists, but also for practitioners working in the field of nuclear energy and radiation protection. The topics raised in the book cover a wide range of issues, including mathematical models, numerical methods, and algorithms that are used to solve neutron transfer problems. The authors explain in detail how multi-group approximation can greatly simplify calculations and improve the accuracy of results. This is especially important in circumstances where many factors affecting the behavior of neutrons need to be taken into account. The book will be of interest not only to specialists, but also to senior students who study nuclear physics and radiation safety. It will help them better understand the complex concepts and methods used in modern research. Also, this edition can be useful for scientists engaged in the development of new technologies in the field of nuclear energy and radiation protection. The style of the authors is distinguished by clarity and logical presentation, which allows the reader to easily follow the course of thought. They use many illustrations, graphs and examples, which makes the material more clear and understandable. This is especially important for complex topics related to mathematical models and numerical methods. The authors strive to make their work available to a wide audience, which is one of the main advantages of the book. Mark Nikolaevich Nikolaevich and his co-authors are known for their research in the field of nuclear physics and radiation safety. Their work has received recognition both in Russia and abroad. In this book, they combine their knowledge and experience to offer readers a unique perspective on multi-group approximation in neutron transfer theory. If you are interested in nuclear physics, radiation safety, or just want to deepen your knowledge in this area, the Multi-Group Approach in neutron transfer theory will be a valuable source of information for you. This book will not only expand your horizons, but also help you better understand the complex processes taking place in the neutron world. Do not miss the opportunity to get acquainted with the work of outstanding scientists who have made a significant contribution to the development of the science of neutrons and their interaction with matter.