@bookstodon Not sure if this is anybody's cup of tea but there's a new Lemmy instance dedicated to books and writing over at: https://literature.cafe
The best part is you can participate from your existing fediverse account. Communities on Lemmy can be followed like users and have similar functionality to a.gup.pe groups!
Try following @fiction as an example but remember that federation doesn't backfill.
More communities can be found here: https://literature.cafe/communities
literature.cafeliterature.cafe - A Cozy Place for Book Lovers, Readers And Writers