THE HUFFINGTON POST chose these.
I am going to go with ROOM by Emma Donaghue. When an author puts you through the grinder as this book did, you need to come away with more hope for a good future for its characters than this book provided. Although the ending may be authentic to life, it's not satisfying as fiction. Even a more vague ending would have been better.
What's your choice for an unsatisfactory ending to a good book?