I finally broke down and bought The Zen of CSS Design. And yes I'm reading it from cover to cover. It's an interesting book on design principles and practices for CSS, using the The CSS Zen Garden as a means of teaching that.
For those that don't know what the CSS Zen Garden is, I highly suggest you click the link above and check it out. Not only does it supply you with a good understanding of the benefits of CSS design it also has some excellent work to showcase that can help you or inspire your work.
So far I'm loving the book. I can't say as I've seen all the designs, but after I've read the book and each of the 36 in the book I will take a look at and also a gander at the CSS used to learn from them, as the book doesn't exactly explain it all, only some of the key elements. But it's a good read thus far, I'm enjoying it.