BookWyrm is a social network for tracking your reading, talking about books, writing reviews, and discovering what to read next. Federation allows BookWyrm users to join small, trusted communities that can connect with one another, and with other ActivityPub services like Mastodon and Pleroma.
I kind of see the idea. When I check some of the higher quality (to me that means evidence backed with an internally coherent logic to new ideas) nonfiction on goodreads/other platforms, especially early, too many reviews boil down to “reading is hard”.
But it should definitely give you a way to expand to “all reviews”, because I can’t see many single servers having enough of a base to be useful on their own.