This appears to be an edition which is an earlier draft. The main concept is there, but there are issues which some parts are clearly missing details, and other parts are just a little unclear. It gives a good view and is somewhat shorter than the released version. It is freely available, and is meant to be. I'm not sure if the HTML or Markdown versions might be more complete.

I honestly really loved the system, and hope to have a look at the full version shortly.