This book is the Bible of paintball. It covers the basics for beginners and runs up through drills for more advanced players, including some interviews with big figures in paintball, like some of the original players who were in the first game ever played, current pro players, gun designers and the owner/operator of Skirmish USA.
A word of caution after having read another review on this page - this book covers a lot, but not individual markers. Very few books cover specific markers and upgrades. That would date the book extremely quickly (see the reviews for Paintball!: Strategies & Tactics by Bill Barnes) and it would be impossible to be comprehensive. If you don't believe me, check out Special Ops Paintball's website - there's already enough there to fill a book, and that's only one company's offerings. The book offers some general guidelines for upgrading your marker, and that's the best you'll get from almost any worthwhile book out there.