I especially like the CSS1 properties list at the back of the book. It gives a clear explanation of each of the properties including which browsers (not including Netscape 6) they work with. Since CSS is not reliable across all browsers at this time, this is crucial for getting a Web site that looks the way you want it on at least the major Web browsers.
Another really useful section is the "Tips and Tricks". Using CSS in the real world involves more than just an understanding of the CSS specification, but also how the browsers interact with the properties and tags. The tips and tricks will help you get your site looking the way you want.
CSS is fun to use, and once you have this book, you'll understand the true power that it provides the Web developer.