Haddix really is a master at middlegrade. She manages to convey mature topics like propaganda and corruption in logical ways, as well as some fairly complex parallel universe ideas. I realized at some point that this is actually surprisingly dark for a childrens book, I mean, mind control, and brainwashing? Not themes you'd expect, and yet they are conveyed very well. It was a good ending I think as well, although my more jaded point of view would say that it was unrealistically positive (or I've just been reading too much YA with tragic endings), but seriously, you're telling me two dimensions signed a peace agreement after like a week, despite our dimension being made up of a ton of different countries? Doubtful.