What a fun read this was! I laughed out loud several times. The characters are charming, well developed and highly entertaining.
Being as the main character is an 11-year-old girl, I would say the target audience is within that age range. Don't let that put you off though, the material is plenty entertaining for adults too. Even with smaller pages and slightly enlarged type, it's a fairly hefty read. Books were never this large when I was eleven.
As someone who has lived in Arizona for quite some time, I really enjoyed the part of the book that took place here. Mr. Rex knows what Arizona is like and did a great job of poking fun at the names and culture of the place.
The premise that the story is intended as an essay for a time capsule, is brilliant and works well with the first person "What I Did Last Summer" sort of story telling. Sprinkled throughout are fantastic "comics" and illustrations by Gratuity's (the girl heroine), alien friend, JLo. Picture the minions from "Despicable Me" and add a bunch of tentacle legs on the bottom and you get an idea of what the aliens look like.
I did find the constant references to the white man stealing the Indian's land rather heavy handed. The fact that the aliens come to the planet and send Americans to live in one state gets the point across well enough. He brings it up over and over again, though. That's a small thing though, and I ding the rating only slightly because of it.