CakePHP Book, Release 4.x covers various core features and functionalities including caching mechanisms such as Redis with fast delete operations using UNLINK, command-line tools for managing applications, debugging capabilities that support stack traces and breakpoints, and the use of plugins to extend functionality. The book also provides detailed information on how to set up development environments, manage migrations, and integrate third-party services.

文档详细介绍了如何从CakePHP的4.x版本升级到5.x版本，包括准备升级所需的步骤、迁移指南以及更新后的依赖项。文档还讨论了各种迁移中的注意事项和新功能的变更。