Designing With Web Standards (aka the "Shocking Bad Hat" book) by Zeldman is recommended by other people, as is Eric Meyers CSS book. Personally, I only used O'Reillys CSS Pocket Reference (also by Eric Meyer).

I haven't read the book but the author's web site displays poorly when given an unusual Mozilla browser. I'd take whatever advice is in that book with a grain of salt.

Any recommendation on CSS books?

Not really. I've found that like the HTML specs, you can learn CSS reasonably well from the w3c docs alone. It helps to have working examples around (especially for layout techniques), but there are plenty of web sites that have those for free.

There are subjects I prefer to find a good book for, but CSS isn't one of them.

Dead tree is ideal for reading when you are doing other work on a computer monitor. But I suppose printers can do :)

CSS has been on my list of "stuff to learn" for a long time. My site is still raw HTML because I haven't had that time

If you write a significant amount of HTML, learning CSS will save you time. You can learn quite a lot of CSS in one day, enough to throw out your legacy HTML deprecated physical markup and never look back. In three weeks you'll have regained the time you spent learning CSS.

There are a very small handful of things you'll still use deprecated markup for, because of missing browser support for the corresponding bits of CSS. Horizontal centering is one. border="1" (or whatever thickness you want) on table elements is another. But the time you'll save that you used to spend just in putting in font tags will pay you back the time for learning CSS in short order. Don't delay; learn it today. You can find a good CSS1 tutorial at htmlhelp, and there's a decent CSS2 tutorial at w3schools.

I have Mozilla bookmark keywords set up for XHTML and CSS to point to the corresponding w3schools pages, so that I can type into my browser's address bar something like "css border" and go straight to the explanation of the border property. When I was first learning CSS I used this a lot.