The Invariance of the Stationary Probability Distribution of Mass-Service Networks with Inactive Applications by Yu. C. Crook is a deep and comprehensive study that immerses the reader in the world of probability theory and mathematical statistics. This work will be a real find for students, graduate students and specialists in the field of mass service theory, as well as for anyone interested in mathematical models and their application in real life. In his book, Crook explores the complex aspects of mass-service networks, focusing on the invariance of stationary distributions. This concept usually requires a certain level of preparation from the reader, but the author masterfully explains complex ideas, making them accessible to understanding. It considers not only traditional models, but also introduces the concept of inactive applications, which adds a fresh look and relevance to the work. The reader will be able to learn how various factors influence the behavior of service systems and how processes can be optimized to achieve the best results. The book will be interesting not only for those who are already familiar with the theory of mass service, but also for those who are just starting their way in this area. Students and young scientists will find here useful examples and practical tasks that will help consolidate theoretical knowledge. Practitioners will be able to use the knowledge gained to improve the efficiency of their systems, whether in the field of telecommunications, logistics or other areas where optimizing the flow of applications is important. The topics raised in the book cover a wide range of issues, ranging from the foundations of probability theory to complex mathematical models. Crook focuses on the importance of understanding stationary distributions, their role in the analysis of mass service systems and their application in real-world scenarios. The book also addresses issues related to predicting the behavior of systems under uncertainty, which makes it particularly relevant in today's world, where data and their analysis play a key role. Style Y. C. Crook can be described as clear and logical, which allows the reader to easily follow his thought. He uses many examples and illustrations that make the material more visual and understandable. Crook is also known for his other work in probability theory and mathematical modeling, which confirms his status as an expert in the field. His previous publications, such as Mathematical Models in Mass-Service Systems, are also noteworthy and may be of interest to those who want to deepen their knowledge. The book "Invariance of the stationary probability distribution of the state of mass service networks with inactive applications" is not just a training manual A true encyclopedia of knowledge for everyone , who wants to understand and master complex concepts in the field of probability theory and mass service systems It will become a valuable resource for students, teachers, researchers and practitioners seeking to improve their skills and broaden their horizons of knowledge. If you are looking for literature on mathematical modeling, probability theory or mass service systems, this book should definitely take its rightful place on your shelf. Do not miss the opportunity to immerse yourself in a world where mathematics meets practice, and theoretical knowledge becomes the basis for real solutions.