Bought this tiny Zen book for $1 at the same time I bought the more comprehensive The World of Zen. This one was an OK reiteration of some of the concepts and even clarified some of them a bit more, as much as Zen can said to ever be truly "clarified." I see this as a quick handy reminder reference at best, probably good as a portable travel companion. It's an attractive little book.
I was unfamiliar with the practice of Zen before reading this, so it was very eye-opening. It’s a short read, but I found it comprehensive. One of the biggest takeaways is that you can most understand Zen through un-reason and as such long,lofty books about zen may not be the best way to understand the tradition.