Goodreads - See what your friends are reading.
LibraryThing - A home for your books.
Riffle - Just good books and the readers who love them.
BookAuthority - BookAuthority collects the most recommended books on business, technology and science - as featured on CNN, Inc and Forbes
GoodBooks.io - Largest curated collection of 8,500+ book recommendations.
Readernaut - We are a small community of readers, sharing our adventures and supporting each other as we persue a life of learning.