It's not often I read a book and feel like I've learnt something new after every page; however this was exactly what I felt after reading Stunning CSS3.
Previously I'd known some of what CSS3 was capable of - rounded borders, box shadows, semi-transparency with RGBA - but I'd not seen such a complete overview of what's new in CSS3, or as many real-world examples of how its features could be used in combination, as offered by this book.
What I liked about this book was the emphasis on progressive enhancement; that we should be striving to give visitors with the latest browsers the best possible experience, while still presenting a perfectly acceptable experience to visitors with less modern browsers. The author did a good job of explaining current browser support for each feature, and how to implement features in such a way that older browsers still render the page nicely.
If I have one criticism it would be that too much time was covered on workarounds for IE6. Sure, cross-browser compatibility is important, but IE6 is ten years old now and any web designer or developer picking up this book shouldn't expect the examples to be supported.
A lot of focus was also given to usability and efficiency, for example reducing HTTP requests by replacing images with styles. You may not think this is particularly important (with broadband speeds now pretty commonplace), but with mobile browser usage growing fast this is still worth being aware of.
The term "responsive web" is this year's buzzword and this book dedicates a chapter on designing for various screen sizes through media queries. Not only is this incredibly useful for mobile designs, but designing for larger screens too (e.g. internet-enabled TVs).
Finally I was pleased that even parts of CSS3 with little or no browser support are covered. The flexible box model was completely new to me and I look forward to being able to use this once all browsers catch up with the spec.
Overall I thoroughly enjoyed reading this book and am itching to start using media queries, web fonts, transforms, and a whole bunch of other CSS3 goodies soon.