A lot of people recommend "Eric Meyer on CSS". Next time you're in a bookstore take a look through it.

I started with "Spring into HTML and CSS" by Holzschlag, and just ignored the HTML half. Even though only half the book was useful to me, I chose it out of a crowded shelf for the clarity of the writing and the examples. Probably not enough detail for you, but one diagram laying out the whole padding/border/margin thing might bring some enlightenment.