The book “Theory of Parties and Party Systems”, created by the team of authors, is a deep and comprehensive study of one of the key areas of political science. This work will become an indispensable companion for those who are interested in the mechanisms of functioning of modern political structures, the internal dynamics of party movements and the features of party systems in different countries of the world. It can be called a reference book for students of political science, politicians, analysts and anyone who seeks to understand how parties are formed and develop, what role they play in the life of the state and society. What is hidden behind the pages of this book? It reveals the main theoretical concepts underlying the party system, starting with classical models and ending with modern approaches that take into account global changes in the political sphere. The authors are not limited to dry definitions and theoretical calculations - they lead the reader through a rich history of the development of party systems, show their diversity and features in different countries and eras. Particular attention is paid to the analysis of such concepts as party competition, party identity, party integration and disintegration, as well as the mechanisms of interaction of parties with civil society. This book is especially valuable because it is not only theoretical, but also practical. It examines in detail the current challenges faced by party systems in the context of globalization, digitalization and changing political landscape. The authors analyze how new forms of communication, social networks and information technologies affect party activities and elections, as well as how parties adapt to new realities. This approach makes the book relevant and useful for those who want to stay up to date with the latest trends in the political sphere. The book “The Theory of Parties and Party Systems” is suitable for a wide audience It will be of interest to students and graduate students studying political science, sociology and international relations, as well as teachers, researchers and politicians looking for a systematic and analytically rich presentation of the topic. Between the ages of 18 and 45, especially those interested in the internal structure of party movements, their role in democratic processes and the characteristics of party systems in various countries, this book will open new horizons of understanding. The peculiarity of this work is its ability to combine theory with practice, providing the reader with not only knowledge, but also analytical tools for assessing current events. It raises important topics related to democratic institutions, party competition, electoral systems, and the role of parties in shaping public policy. The authors use rich historical material, modern cases and comparative analysis, which makes the book not only a textbook, but also a valuable source for professional research. The author's team, with rich experience and expertise in the field of political science, created a work that is distinguished by clarity of presentation, logical structure and wealth of examples. In the style of the author, academic rigor is felt, but at the same time the book is read easily and interestingly, which makes it available even for those who are just beginning to get acquainted with party theory. Among the well-known works of the authors, one can distinguish their research in the field of political system and comparative politics, which gives the book additional authority. If you are looking for a book that will help you understand how parties are formed and functioning in the modern world, why some systems are stable and others are subject to crises, and how parties affect the fate of states, the Theory of Parties and Party Systems will become an indispensable source of knowledge for you. This book is not just a textbook, but a guide to the complex and exciting world of political structures, revealing the secrets of their internal logic and external manifestations.