The Curse of the Ancient Mask and Other Case Files — Simon Cheshire

Saxby Smart is no ordinary school kid. He's the best detective in the world, or at least the best one who also happens to be in elementary school. In this brand new series--with three cases in each book--the reader solves the mystery alongside Saxby, getting peeks at pages of his casebook as the crimes unfold, and searching for clues rather than letting the main character do all the work and have all the fun.