One I started reading recently: "Search Engine Optimization: An Hour a Day," by Jennifer Grappone and Gradiva Couzin. It's fairly good.
But, I have to tell ya, that as far as
SEO books go, the best one I have come across is Planet Ocean's ebook (
Search Engine News - Search Engine Marketing Strategies from Planet Ocean). Aaron Wall's book follows that (though it is a bit less readable). Both are updated regularly. If you're tired of reading them on your monitor, just print them out and put them in a binder. Happy reading!