
Design Thinking by Ellen Lupton will help with concept development, sketching, and research. I'm reading Graphic Design Process by Skolos & Wedell right now and I would recommend that too.
If you ever want to learn more about advertising, creative ideas, strategies and concept development, read The Advertising Concept Book by Pete Barry, it's surprisingly big.
I would also include "The Advertising Concept Book". To me a website is an ad. This book actually shows what worked what didn't - ads from the last 40 years for the masters. I love sketches to actually ads run. A lot of analysis on Apple ads. It was just an awesome, eye-opening book. So many case studies.
Side note; I think of account about typography in one of the books about FLICKR. Where if you were not careful what type you choose you would very much offend many people since the capital L and I might merge to be U.