Learned a lot of cherry-picked strategies for solving specific web design problems using CSS. I appreciated the cookbook format, in that the solutions target and explain how to solve specific problems, clearly stated and illustrated with real-world examples from Lea Verou's sites and others' professional websites.
The biggest pain points that this book helped me solve were
3. Flexible background positioning
9. Flexible ellipses
10. Paralellograms
11. Diamond images
12. Cutout corners
31. Custom checkboxes (toggle switches)
40. Vertical centering
43. Frame-by-frame animations
Most of the geometry strategies also extend to solving other problems, like shadowing and gradients for achieving visual effects.
Even an obscure, seemingly useless section like "Fancy ampersands" contained ideas I could apply to other CSS problems, like using unicode-range and fonts with limited character sets (digits, symbols, etc.) to pad font stacks with better-looking numbers.
My main issue with the book isn't so much the selection of strategies and the divergence from them, but rather the lack of explanation for code. Terms like "pseudo-___" (pseudo-elements, pseudo-class etc.), dd/dt, :not, first-child, and many other obscure CSS terms receive no explanation whatsoever. It annoyed me how many non-English terms were thrown around without definition or even a quick aside. Instead, space and time are devoted to wasteful cat jokes and snide remarks like "you might expect..." My suggestion to Lea Verou would be twofold:
1.) Define key terms (pseudo-element) the first time you use them, to establish a common baseline of understanding;
2.) Comment individual lines of code (add a graphic or ← to the right of each line, explaining what it does.)
Otherwise, much of what I read went in one ear and out the other, because it didn't stick why I was doing it. Ultimately, I had to experiment with the code in an editor like Nova, toggling lines on/off to see what effect they had. The illustrations help, but the code snippets in the book show too large a chunk/block without line-level explanations to be truly understandable.
Still a useful book nevertheless. I would just supplement it with experimentation and more detailed reference texts, like CSS: The Definitive Guide!