There are many Goodreads competitors. To the others already mentioned, I'll add https://inventaire.io/ https://inventaire.io/ , which is fully free software and

There are many Goodreads competitors. To the others already mentioned, I'll add https://inventaire.io/ https://inventaire.io/ , which is fully free software and based on open data (Wikidata). It's useful if you want to have full control on your own book catalogue while not having to produce all the data yourself.