Comment by Meleagris

I was looking into this space the other day, and the number of options has been growing. By my record there is:

- https://www.goodreads.com

- https://thestorygraph.com

- https://fable.co

- https://hardcover.app

- https://joinbookwyrm.com

I was actually trying to determine the best free source of metadata for books. I was hoping for something like MusicBrainz.

The best I could find seemed to be https://openlibrary.org. There is https://isbndb.com, but it is paid.