Something I've been dabbling in and thought I'd better find out about properly.
This is a "typical" O'Reilly title (which is a good thing, BTW). Good discussion of the basics to get you thinking right, then lots of examples and a good coverage of the kinds of things you want to do. Then there's the reference section in the back.
Of course CSS is changing (this book covered CSS1, with a "look ahead" to CSS2), so look out for revised editions.
My rating: Recommended