The book "The Haskell Textbook" is a source of knowledge for those who want to master functional programming in the Haskell language. The book explains in detail the basic principles of working with Haskell, its syntax, basic concepts and programming paradigms. The authors expand from the simple things, gradually moving to more complex concepts, allowing readers to absorb the material gradually. The book contains many code examples, tasks for self-solving and is structured in such a way as to lead the reader step by step to understand the depths of functional programming. The Haskell Textbook is an indispensable resource for beginners as well as experienced programmers who want to deepen their knowledge of functional programming.