I like RethinkDB a lot. One year ago, I started to document it because I want to learn more about it. At first, I blog, at one point I started to writing it in markdown, using pandoc to convert it into PDF then I switched to Leanpub.
At some point, I almost abandon it. But finally I make effort to go back and almost finish it.
Here is the result of one year:
http://leanpub.com/simplyrethinkdb
I also open source it on here(But it helps if you make an purchase on leanpub anyway :D):
http://github.com/kureikain/simplyrethink
The book is still WIP though.
It would be great if someone can help me to review it, or/and write a foreword for it. drop me a line, my email is on github.
Thanks.