The best reference guide to learning CSS I've read so far. Goes beyond basic principles into much more complex design techniques and mathematical coding structures such as inheritance and pseudo-classes. Also has a well-organized and extensive CSS properties chart in the appendix, which is perfect for quick reference.
I still don't think I'd be able to learn CSS from the ground up just with this book alone, but that could just be me (I don't really learn from written material). For me, it's a perfect guide to use with hands-on projects and material. For someone with an established background in computer languages, you probably could learn CSS with this book alone.
Highly recommended for anyone starting out in the field. I'd say it's intermediate-level material.