509
The Fediverse
(links.hackliberty.org)
A community to talk about the Fediverse and all it's related services using ActivityPub (Mastodon, Lemmy, KBin, etc).
If you wanted to get help with moderating your own community then head over to !moderators@lemmy.world!
Learn more at these websites: Join The Fediverse Wiki, Fediverse.info, Wikipedia Page, The Federation Info (Stats), FediDB (Stats), Sub Rehab (Reddit Migration), Search Lemmy
I don't think you can correlate the number of readers to the number of book instances or whatever they're called. Most people (myself included) probably just use Goodreads, and BookWyrm is probably a good enough alternative that there's no need to spin up another.
Edit: according to this there's a lot of instances: https://joinbookwyrm.com/instances/