Goodreads
https://www.goodreads.com
aNobii
Babelio
BookArmy
Bookish
douban
iDreamBooks
LibraryThing
Open Library
Readgeek
Shelfari
The StoryGraph
Library 2.0
the concept behind Goodreads and similar sites
https://ja.wikipedia.org/wiki/Goodreads
https://en.wikipedia.org/wiki/Goodreads