This is book is a "copy" of JUnit5 documentation. It nearly describes what JUnit framework is, but provides almost no author insights of practical application - almost no examples where particular JUnit concepts can bee applied in real life project. On top of that book is extremely short and majority of the book content is either code or screenshots. You can clearly see that book has been rushed to market.
If you know what JUnt framework is and what it does I would recommend read documentation instead of this book.
this book is only good for the Junit introduction and junit features in detail but if your goal is to write actual test cases using Mockito or some other libraries, then it is not the good choice. Also this book does not cover test cases for code written in some frameworks like Spring. only high level test cases for your some utility classes.
It's good overall. - On the bright side, it helps me to learn basic and advance things that does not usually metion in the video course. - but on the other hand, some hidden parts interrupt the following. I got stuck a lot and had to view the source code to see which part was missing.