Goodreads - See what your friends are reading.
Reese’s Book Club - Every book, everyone’s invited
LibraryThing - A home for your books.
Four Hour Book Club - 300+ Books recommended on the Tim Ferriss Show 📚
BookSloth - Book Sloth lets you add books, post and see reviews as well as interact with other readers.
Bookself - The social reading app 📚💬