Non fiction, I don't really rate them usually but this should be required reading.
 I had not heard of this until it was recommended by books that matter, and oh my am I glad I read this.
I only wish I had read this years earlier than I have. 
It took me a little while to read the 110 pages as it gets through some quite hard topics in a very short space so I found myself taking a break from it, but yes, I would 100% recommend this.