I adored this book and will be suggesting it for many of the upper grade readers at my school. The two things I loved the lost: 1) how a grown up man captured the tone of a 13 year old girl so perfectly and 2) how none of the usual suspects of characters that could turn against the girls did. I was prepared for that being the experienced, cynical reader that I am, I even had picked out the adult I thought would be using them, but it didn't happen, and I applaud the author for that! It's just a good, fun read and I loved trying to solve the puzzles along with the girls. Can't wait for book 2!