Learning theory will help you put all the pieces of the musical puzzle together. Why do some songs have similar chords? Why does my favourite guitarist use that scale in that song? The idea of this book is to answer the questions you might have and to demystify music theory.
There is sometimes a reluctance amongst guitarists to learn theory (or learn how to read music). I've heard the arguments many times and usually there is a fear that knowing how things work will reduce the magic. I can appreciate that but the idea here is to understand things so you can make the magic work even better. Knowing music theory shouldn't impact negatively on your creativity - you need to learn the rules so that you can break them.
Just like you practice how to play your guitar you will need to work on the theory concepts presented here. Try to work them into your practice regime - you could use the circle of fifths to practice your scales or you could call out the names of the notes when practicing your scales.
It's not necessary to read this book cover to cover in one go. You might want to tackle one chapter and take some time to work on it and make sure you have properly understood all the concepts involved. While the information I am setting out here is fact I would encourage you to test everything that's in this book. This will help with retaining the information and also help to make sense of it. Equally you don't need to read the chapters in order although some ideas are explained in sequence, if you want information on dominant chords you could skip to that chapter.
Where appropriate I have included the names of other chapters that might contain relative information. You don't need to be able to read music notation to use this book. I have avoided using music notation symbols and have only used some in a couple of examples purely for reference. Of course if you can read music this knowledge will be of benefit and should reinforce the information here.
If after reading this book you have a theory question that you feel wasn't answered you can contact me by email using firstname.lastname@example.org. Every scale and chord are not listed in this book, there are numerous books and apps that have that information. Learning the theory will help you decipher the information that these book/apps provide.