Music theory is something I intend to teach more and more. I feel like a good basic book about this topic would be a great companion for all students on my website. I admit that I have not yet found the "perfect" book. I might have to write my own one day. 

Let me ask you, is this assumption by myself correct?

• You want to learn more about chords and scales and intervals and how these things work
• You want to be able to apply that knowledge to the fretboard
• You want to be able to to use a variety of music theory concepts to play with more variety

Does that describe you? I think many of us are in that boat, and I feel like written material is necessary to keep referring back to, as we learn these concepts and apply them to the guitar.

Here is a free book. I have not gone through it yet, but it might be worth a look. Let me know what you think, if you go through it.