But something went awry—I'm not sure what—and the project was allowed to languish by Google. The interface has been in maintenance mode for ages, with no development going on. This leads to a lot of frustration: for instance, you cannot share all of your saved and tagged books with another user, and sharing a shelf or series of shelves is awkward and clunky. In terms of UX, it appears to be abandonware.
On top of that, there's no way to know what's going on or who to talk to, because users can't actually contact anyone at Google Books.