Title: My Teacher is an Alien
Author: Bruce Coville
What it's about: *obligatory pun about the teacher being "out of this world"* Anyway, the plot's pretty simple. When Susan's sixth grade class gets back from spring vacation, they find that they will be having a substitute for the rest of the year, a strict and boring guy named Mr. Smith. Susan finds out that Mr. Smith is really an alien, and she confides in the only person who will believe her, the class nerd Peter Thompson. Together they uncover the alien's plan and get the rest of the class to help them thwart it.
What I thought: For being science fiction aimed at middle school kids, this books holds up pretty well. I was surprised at how many genuinely funny bits there were. The plot isn't very complex, but it's just right for the length of the book.
Overall: An excellent piece of children's literature.