I have written 24 really practical guitar eBooks as well as 2 FREE eBooks! All are easy to understand and can be applied to your guitar playing today. And you can purchase them for Amazon's Kindle, Kobo and Google Books.
The Basic Series is a great starting point, especially if you're a self-taught guitarist. You can purchase either a single topic focused ebook or the whole basic series collection.
When you've built a strong foundation, then move on to the Advanced Series. All of these eBooks are designed to enable you to develop your guitar playing quickly using advanced ideas. In addition to single ebooks, you can purchase the whole advanced collection.
If you're still unsure, then start with the free eBooks, as both give you a taste of the full ebooks.