Molly Fyde and the Land of Light  (The Bern Saga #2) - Hugh Howey
Absolutely fantastic. You got mystery, adventure, bravery, sacrifice, love, betrayal, a great cliffhanger ending.... but none of that is the best part. The best part is the imagination that went in to telling this story! It's so unique--nothing I could have imagined up myself in a million years. I love that about Hugh Howey!

Plus, this is a perfect testament to my policy of not starting a series until all the books are written and I can read the whole series at once. These are the biggest cliffhangers I've ever experienced. Waiting for the next one would kill me!