Not having kids of my own, I judge these books based on how I would have enjoyed them as a kid. If I still had my spiral notebook where I kept track of my many Nancy Drew and Sweet Valley High books, I would have chosen the fuschia color from my multi-ink click pen and drawn in rounded script the title of the book followed by five shakily drawn stars (By the way, I still haven't mastered the art of a perfect star shape). 
 Emily Crane's parents have vowed to live in all fifty states. This means Emily never really grows roots into any one place or ever makes any really good friends. Her constant companion is Book Scavenger, a treasure hunt where players score points for both finding and hiding books, using their online profiles to track their progress. 
 The Crane family is on their newest adventure, moving to San Francisco, which also happens to be the headquarters for Garrison Griswold, creator of Book Scavenger. His newest game is to be unveiled that afternoon, but is never announced as Griswold is involved in what's believed to be a mugging and is in the hospital. 
 Not long after this Emily, along with her brother Matthew and neighbor James, come across flowers and get well cards left at the subway sight where Griswold was attacked. While bending down to retrieve some trash that didn't make it to the can, Emily sees a book crammed between the can and wall. She is convinced that the book must be part of the scavenger game. What she doesn't know is that she isn't the only one seeking that book and this will lead her on a quest to solve the puzzle before anyone can take the book away from her. 
 What follows are lots of really fun puzzles and code breaking with themes of family and friendship interwoven throughout. There are a few sections that ask the (ahem, older) reader to suspend belief, but it never takes you out of the story. I would not hesitate to recommend this to any reader, young or old. And bonus - there's already a Book 2!