Among all the web-related disciplines, search engine optimization (SEO) surely has the greatest volume of conflicting information. In a field filled with everything from bad advice and outdated information to outright scams, it is hard to know what to believe.
We've just read one of the newer books on the topic, Outsmarting Google by Evan Bailyn, and we recommend it highly.
Evan doesn't shy away from giving specific advice, and his opinions seem solid. He's done the experimentation and had the experience to be able to make meaningful suggestions about things that just aren't knowable from the little that Google discloses, without going into snake-oil or black-hat territory.
The book is also quite up-to-date, covering the differences between the Bing/Yahoo and Google algorithms and other recent developments.
If you're looking to improve your SEO knowledge, this book is well worth your time.