@eldang Library Thing and Open Library. the first one is a lot like goodreads and has a pretty big community from what I've gathered, and the second one seems to be just getting started on the community aspect and doesn't have a lot of users. plus I think, you'd need to add some books yourself.
I'm trying out Open Library a bit right now but I don't know yet that it's a good alternative (and I don't much like Library Thing UI, so I haven't tried it yet)
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