The Puzzling World of Winston Breen - by Eric Berlin

If you love solving puzzles and mental challenges of all sorts, this is the mystery novel you're looking for.  There's hidden treasure, a cranky librarian, shadowy evildoers, tasty pizza, and a retired police officer who doesn't seem to realize he's retired.  It all begins when young Winston, the puzzle-loving genius, finds a used wooden box with a fake bottom containing clues to a grand mystery. The only problem:  He gave the box to his sister for her birthday, so the clues belong to her.  Before long, the two of them join up with an unlikely cast of treasure hunters in a race to solve the mystery.  There's danger, trouble, and intrigue, but there's also that pizza I mentioned.

This book is FULL of puzzles, some part of the story, some just tossed in there, with answers to all of them at the back of the book.  Luckily, even if you decide to skip the puzzles, you'll have no problem following the story. The plot is a relatively straightforward mystery, but it's interesting enough to be worth reading.  You can definitely tell it was written by a puzzle geek, but that's what makes is good for the puzzle-loving upper-elementary or middle school reader.