A draft of the first chapter of the ZODB book has been committed to our GitHub repository. It's just the introductory chapter, so it might not seem like much. However, the introduction is very important when starting a technical book, since it sets the tone and helps define the audience more clearly.
If you can spend a few minutes to read it and comment, that would be very helpful.
By the way, there is now a portlet at the top right of the blog that shows the latest commits to the repository. This may make it easier to keep track of the book's progress.