The Emperor's Code by Gordan Korman

In the latest entry in the 39 Clues series Dan and Amy go to China. Although they're separated for most of the story, they slowly but surely come to realize whom they can trust. I really liked the chance to see more of Jonah Wizard (whose appearances are amusing). I'm also increasingly intrigued by Nellie--she's clearly serving two masters, and it's strange that Dan and Amy (who are usually so sharp) haven't quite put it together yet. I'm eagerly awaiting the last two books in the series.