When you buy a book, you're tapping into what makes that particular author tick and their years of experience, all without having to go through the hassle of "maybe" being able to talk to that person and ask them questions in person. The value of books is really apparent when it comes to learning guitar.
Like any other subject though, it pays to know what books are great to begin with, so you learn the best stuff first. I've collected a list of some of my favorite guitar books, from beginner to advanced. These books focus on not only making you a better guitar player, but a better musician overall.