Does anyone own this? Is it a worthwhile series to learn the fretboard, is it thorough? It seems to me that it's the only "complete" set to fretboard theory while other books just focus on some specifics. I am hesitant to trust the ratings on Amazon.com as I am unaware of their guitar capabilities. Anyone who first picks up a guitar will give it 5/5 stars.

Here's the link.

I've never seen volume III, so I can't speak to it, but the first two volumes do a good job of teaching CAGED. If you need help learning the fretboard, this book can help you. Another good book is Guitar Fretboard Workbook by Barrett Tagliarino. It's a true workbook, lots of exercises you have to work out yourself.
I'm not expert on this, I've just started to learn guitar but a while back I bought the set, vols. 1-3, and in my opinion it's pretty good.

Volumes 1 focus is on teaching you the CAGED chord sequence, then you go onto CAGED scale sequences and lead patterns. The idea the book tries to get across is that you learn the chord/scale shapes CAGED and you can use those to navigate the entire fretboard.

Volume 2 goes into chord construction, arpeggios and modes, and there is a little theory thrown in as to how it applies to the guitar fretboard.

Volume 3 is about application of these things, rhythm articulation and other techniques and some theory, just as it applies to whatever the lesson in that chapter is.

I would say that the set is really reference material, but from it you learn the basic framework on which to make music with. It's totally easy to read and follow, totally worth getting in my opinion, but I'm just a noob so I have nfi what I am talking about.