I wouldn't let the fact that the book is in beta dissuade you from getting it. It's mostly feature complete and is a _fantastic_ resource - it really helped get Ash to click for me, and I've found it a joy to work with after getting that initial ah-ha moment.

I know the Ash team is aware of the documentation challenge, and they are working on it. I feel like the book is an answer to that, and hopefully a lot of the greatness of the book is able to make its way back to the docs.