Hi John,
I would personally recommend picking up a book on HTML & CSS. I haven't looked at w3schools' tutorial on CSS, but a general advice would be to stay as far as possible from that site. From what I've saw and read from others, they often teach bad habits.
I can't recommend any book though, because the one that I've used wasn't in English.
Edit : Now that I think about it, buying a book on HTML & CSS for the sole purpose of making ebooks would probably be overkill, especially time-wise. In this case, I would recommend something more like this tutorial. It's free and seems very high quality.