Paperback. Very good condition. From the back: "See, we're mostly just good friends who go to school together, eat lots of ice cream, and - oh yeah! - we're forming a band. And then there are scooter rides with a certain boy ... but I probably shouldn't mention that. But I can tell you what else we're working on: tracking down the someone who's been breaking into our school (and cleaning it!), cracking a slew of codes and clues that are suppsed to lead us to a valuable violin (probably stolen!), and finding yet another missing violin (definitely stolen!)."