There is this book called CSS The Missing Manual, by David McFarland. Although I did not finish it, I started it with regards to learn CSS properly (like you)

There is this book called CSS The Missing Manual, by David McFarland. Although I did not finish it, I started it with regards to learn CSS properly (like you) and started to grasp some basic concepts (could not finish it though, due to procastrination). Honestly, I think the books delivers , maybe you could use it!