My brother is trying to learn CSS and asked me what the best book is on the language?

I have obviously looked through the sitepoint books, and I even have one on CSS (Dan Shafer's HTML Utopia), but my brother is on the other side of the planet from me, so he needs to buy one.

I'm asking people not to be biased and give their honest opinion on the best book for a beginner. We all love sitepoint, but if you feel that another book is better/easier to learn from, please do tell.