"Refactoring: Improving Existing Code" - a book written by Martin Fowler, is the bible for programmers who value quality and efficient code. In this book, the author examines in detail the methods and techniques of refactoring - the process of improving software code without changing its external behavior. The reader will receive practical tips and examples that will help him improve his work with the code, make it more understandable, efficient and easy to extend. The Refactoring book has become a programming classic and helps developers of all levels improve their skills and improve the quality of their code.