If you are looking for an open source docker book, check out https://github.com/kencochrane/docker-tutorial I'm building a Docker Guidebook, that I hope to release as a free ebook.

It is on github, and pull requests are welcome. It is currently written for Docker 0.5. I will keep it up to date, and when we hit 1.0 I'll look at getting some hard copies made, if there is a demand.

I still need to pick a license, not sure what is best for a book, open to suggestions.