Money enough for one book on Shibari. Two Knotty Boys, or Shibari Vol 1

As the title says, I've got an Amazon gift card here I need to use, and I'm getting started on Shibari. I'm torn between 'Two Knotty Boys On The Ropes' or Douglas Kent's 'Shibari Vol 1 (Land)'.

Both have excellent reviews, but I'm not sure which is the best for a beginner, and which gives the most indepth information.

The biggest thing in favor of Two Knotty Boys is that there's a Kindle version available.

Any thoughts or experience with these books?