The mystery was kind of interesting, but I figured it out for the most part from the beginning. The hints seemed a little obvious to me, but I'm not exactly the target audience either.
I felt a bit for Cass when she talked about being the odd one out in the family, because it did seem that way at times. At the same time, I didn't quite understand how this feeling made her so obsessed with the drowned city. I definitely understand thinking it's interesting, but she seemed bitter and angry that the town was drowned, though it seems pretty reasonable to me.
The Nutshell: I don't really have too much to say about this one. I probably would have enjoyed it well enough when I was around Cass's age, but I've always been into fantastical stories more. Had the book been much longer, I probably would have been bored, but it was a quick enough read.