I'm happy with all that I've learned from Aaron Wall's SEO Book. It tackles the theories and practices of search engine optimization. It is easy to understand and is very much applicable to the setting of the internet. Even until now, its core lessons are still very important and have influenced the way I market my websites on the internet.
I found it easy to understand, and yet the knowledge it provides isn't lacking. It includes just enough technical details for better understanding, but is also understandable for someone who doesn't have much grounding in the way a search engine is actually programmed.
All in all, I would highly recommend SEO Book for anyone wanting to make a serious effort in promoting their websites or e-business.
Buy this book! Highly recommended!