Charlie Bumpers vs. The Squeaking Skull
This is available as a two CD audio book as well.
The more I read of Charlie, the more I like him for a good series for younger readers. Figuring out what to be for Halloween and worrying about what friends will think if movies scare you are two very valid elementary school concerns. I don't know if I will buy this third book (Halloween is a completely different affair in middle school), but it is certainly a must have for elementary libraries.
Other titles in this series include Charlie Bumpers vs. The Teacher of the Year, and Charlie Bumpers vs. The Really Nice Gnome.