Java Cookbook by Ian Darwin looks to be taking a beginner with core understanding of Java to more in-depth appreciation of things under the hood and standard & third party APIs. Additionally Ian have added modern features of Java viz. JShell and its usage for trying out Java expressions and APIs quickly. Automating several development tasks, in general with this book author's promise looks to be to make the reader (already initiated Java soul) more effective.
Author have nicely compiled the problems and solutions, but IMHO to keep the momentum to finish the book (cover to cover) one need to be really interested in those problems! beyond general language features and standard API related problems reader need to have some personal or official project to spark his/her keen interest. For example the chapter on Java being used in data science and communication with R a reader with some background in same will able to appreciate it more. But having said that, reading these problems will also inspire any reader to use the understanding in the projects! ultimately improving the effectiveness.