Integral Theory is a fascinating and profound work written by renowned mathematicians Stanislaw Sachs and I.. C. Berezin, which immerses the reader in the world of mathematical analysis and integral theory . This book will be a real find for students, teachers and anyone interested in mathematics at a deeper level. In Integral Theory, the authors seek not only to explain the basic concepts of integration, but also to reveal their philosophical and practical aspects. They explore how the integral serves as a link between different areas of mathematics and physics, as well as its role in solving real-world problems. The reader will be able to learn about the different types of integrals, their properties and application, which makes the book useful for both theorists and practitioners. The book will be especially interesting for those who study higher mathematics, as well as for those who want to deepen their knowledge in the field of analysis. Students of mathematical and engineering specialties, graduate students and teachers will find in it many useful ideas and methods that can be applied in the educational process or scientific work. Even those who are not a professional mathematician, but are fond of this science, will be able to learn a lot of useful and interesting things from the book. One of the key topics raised in Integral Theory is the relationship between integration and differentiation. The authors explain in detail how these two processes are interrelated and how they help in solving complex mathematical problems. The book also addresses the issues of the existence and uniqueness of integrals, which is an important aspect for understanding more complex theories. The style of writing of Sachs and Berezin is clear and logical, which makes complex concepts understandable. They use a lot of examples and tasks that help the reader better absorb the material. This approach makes the book not only a textbook, but also a fascinating reading for anyone who wants to expand their horizons in mathematics. If you are interested in works such as "