These are the books that left me with my mouth open:
1.- Timbuktu by Paul Auster. I've chosen this book because the end of the book was completely unexpected and surprising. So, I have to tell that made me open my mouth :O
2.- Auggie Wren's Christmas story by Paul Auster. Again, another book by Paul Auster. Well, in this case it's a little different than in the previous book. Paul Auster tells such an amazing story that it deserves to read it :)
3.- Anya's ghost by Vera Brosgol. Very good story. It happened to me the same as in Timbuktu. I didn't expect anything and Brosgol shows you a world and then, things changes completely.
4.- Angels and Demons by Dan Brown. One more time I didn't expect the story in that way and I found myself woth my mouth open in amazing.
5.- The Witches by Roald Dahl. In this case, the whole story is very gripping, so you are basically expecting anything can happen. Very surprising story with a surprising end.
6.- The vanishing of Katharina Linden. This book is similar to The witches because it catches you from the very beginning. Very good book with mystery which let you with your mouth completely open.
7.- Looking for Alaska by John Green. Well, this book is very good and it has a kind of mystery which I left me with the mouth open.
8.- Never let me go by Kazuo Ishiguro. Everything in this book is a mystery, everything isn't what it really seems, awesome book.
9. Juniper Berry by M.P. Kozlowsky. Another book with mystery included which can't leave you indifferent. Great story.
10.- Harry Potter and the Chamber of Secrets by J.K. Rowling. Last but not least, the mystery of this book is the most I enjoyed. Very gripping ans surprising.
Well, this is me but what about yours?