Hacker News Reader

Is Librarything still a thing?

It seemed promising when it launched, but I switched to Goodreads (before the Amazon purchase) and haven't been able to find the time to look for an alternative since.

For what purpose exactly?

There is one based on ActivityPub called BookWyrm.

https://joinbookwyrm.com/

There's also OpenLibrary by the Internet Archive:

https://openlibrary.org/

Folks seem to be using StoryGraph these days.