Staying on the topic of books I thought I'd share something that I've found to be really helpful.
The reason I believe this art book by James Gurney stands out so well is that it focuses on the approach to an illustration rather than a step-by-step techniques. Which those can be nice to help understand how a particular artist works. But it can be difficult sometimes to take away anything useful from the book that relates to you and the medium you work in. James hits on a large variety of topics and doesn't spend page after page boring you with one subject. Great information short and to the point. His next book, Color and Light is due out this November. Can't wait