Whole lotta typos and lack of technical editing make this not great.
On top of that, there's not really much more than you'd get from any random reference. It's basically "start from here" (not necessarily the right place), "make these changes" (not necessarily the right changes) "and you'll get this" (more or less). Then there's a "How it works" section which is short and doesn't really explain anything.
The chapters are named, I think, to sell copies. Like "Look and Feel Customization" doesn't really talk about look-and-feel customization, but how to use more components, just like the previous chapters.
Not really about "mastery", it's more of a thing you could pull out if you wanted to do a very specific thing as didn't find the 40 examples on the first page of a web search helpful.