I think that the GITenberg collection contains all of the books in PG. At this point, the creation of new repos is automatically done when Distributed Proofreaders creates a new book in PG. Originally, I didn't include around 400 PG books due to their creators claiming copyright, and didn't include Bruce Sterling's book because he wouldn't let me re-license it creative commons rather than his pseudo-public-domain license.
Not much has been happening with GITenberg itself in the past few years. But luckily, a lot of the concepts and code are getting upstreamed into PG. Which in my opinion, is way way better.