Loved, loved, loved this. Really cared about the characters and wanted to know where their adventures led them. The creepy photos add something to the story, but I don't think it would suffer without them. 
 Audience: upper teens, young adults (like, 18-25), and full-blown adults--a lot of crossover appeal. 
 A little disappointed that there's a sequel in the works--I liked the somewhat ambiguous ending, leaving off mid-story, before we see an epic Good vs Evil battle. 
 Also, maybe I wouldn't have loved this so much if I weren't so burned out on dystopias? But right now I think it was fantastic.