The explanations are simple and straight-forward with plenty of code snippets and practical samples in VanillaJS that you can re-use in your own projects. It made me think and answered a lot of "whys". The chapter summaries are also well-written. The style of the book & the terse code samples reminded of my favorite C# book C# in a Nutshell. I have heavily highlighted points in both the books for future reference and to me they exemplify how technical books should be written.
The only nit I can pick is not with the content but with the formatting of the code in the PDF version. Due to unwanted spaces within the code, you cannot copy & paste the sample as is if you want to try them out. I had to use the code samples from the online HTML version. The code samples for only a few chapters are available for download at the author's code sandbox but this isn't really an issue.