Bookstash - Bookstash is a free library of curated summaries from top nonfiction books.
Goodreads - See what your friends are reading.
wits.io - Weekly book summaries recommended by founders and makers
LibraryThing - A home for your books.
Instaread - Read or hear key takeaways of any book in minutes
BookAuthority - BookAuthority collects the most recommended books on business, technology and science - as featured on CNN, Inc and Forbes