The Total Dirt Rider Manual
This is a great book for beginners and advanced riders alike. It's got dozens of short easy tips on a wide range of subjects, all in full color. It has a lot of things I've had to search around the web for all in one place (like a checklist of what to carry with you on the trail). Quite frankly, I can't understand how they can sell a book so inexpensively considering the quality paper and full color printing. I haven't read the book cover to cover yet, but so far, I think it will be a reference I will refer to throughout the years.