I've updated the web site to include progress bars for each of the books in the series. So far there are four books, the first of which is already available on Amazon. The second and third books are already written, but need some polishing before they're ready for prime time.
I'm currently working on the fourth book, and am about a fifth of the way through the first draft. I'll be updating the progress bars for each book as I go, so keep an eye out!