Refactoring: Improving the Design of Existing Code

Nowadays, with the support of refactoring tools for example ReSharper, how to refactor is dramatically simplified especially the simple ones such as Rename and Extract Method, however, knowing the importance that refactoring is to software maintenance and what kind of code needs treatments make a developer stick out from the crowd. Refactoring: Improve the Design of Existing Code is such a book that articulates not only the steps to refactor (How), but also Bad Smells (Where) and the reason behind (Why) with remarkably clear presentation, along with excellent nuts-and-bolts advice. Regardless your experience and knowledge of software craftsmanship, you will surely benefit from this fantastic book.

Despite that you can find lots of useful resources online such as https://refactoring.guru/refactoring and Martin Fowler's (the main author of the book) refactoring catalogs https://refactoring.com/catalog/, it's still highly recommended you read the book thoroughly and systematically, which I'm sure will be a great experience.