"CSS Master" is a good light read book about CSS practices.
It starts off very off-putting, in my opinion. A book for CSS mastery starting with selectors without actually going into selectors performance optimization is a really weird concept to me.
Either way, after the first "Selectors" and second "CSS Architecture and Organization" chapters, the book starts to go into a more mastery-ish direction.
"Debugging and Optimization" starts like a kitchen sink and goes through too much stuff at once for the most part. But the biggest highlight in that chapter was that the importance of "Timeline" has been accented and briefly explained. If you wish you can start learning more on your own from any of the browser's docs.
Learning what repaint and reflow is, is very vital. The book does a good job at explaining the performance penalties with both.
"Complex Layouts" is also a good chapter. Flexbox is the highlight there. Definitely check it out. Perhaps skip directly to Flexbox.
"Transitions and Animations" is not as applicable as the others depending on the project and CSS you do in your own time, but it's a very good chapter nevertheless.
Other chapters weren't that important/useful to me. Especially not "Preprocessors".
Perhaps "Using CSS with SVG" is the best from the rest. Learning how to use both is a must if you want to do "performance-driven" DOM graphics.
Still a 3/5 for the book. It's imo misleading in meaning of mastery and has few chapters that can be expanded such as the "Debugging and Optimization" chapter instead of a "Selectors" chapters at all.