inventaire.io - Keep an inventory of your books. Share it with others. Discover the books available in your network!
Goodreads - See what your friends are reading.
LibraryThing - A home for your books.
readng - Reading lists, book tracking, reviews & stats!
Riffle - Just good books and the readers who love them.
GoodBooks.io - Largest curated collection of 8,500+ book recommendations.