I got my introduction to Rebecca Stead when a friend mentioned enjoying her previous book, 
 When You Reach Me 
 . This book has much the same flavor as that one: the city setting, the slice-of-life look at what it's like to be a kid, constant minor mysteries. This one also has a twist at the end that will make you want to go back through and read it again to find all of the clues that must be sprinkled throughout. I would recommend this book to all liars, spies, Scrabble players, and people who enjoy good solid elementary/young adult literature.