This was both deep and kid-friendly at the same time. At first I was thrown off by the structure - especially the mystery person talking to me on Valentine's Day. But I got used to it and enjoyed how everything tied together. Stead really gets kids this age and the world for them right now, and passages reminded me of this over and over. 
 I agree that this does skew older than her other more middle-grade titles, and the cover doesn't help to indicate the difference. I might not choose it for my fourth-graders, but I think it's good for probably fifth grade and up.