I was at the bookstore the other day and ran across Smashing WordPress, by Thord Daniel Hedengren.
The more I read this book, the more impressed I am.
Just as impressive, however, is Hedengren’s Notes Blog Core WordPress theme. It’s basically a simple theme (although it does have one faux-flashy oddity) with a clean appearance and a fast load time.
If you’re looking for a great book on WordPress, a nice clean WordPress theme, or both, check out the work of Thord Daniel Hedengren.