This is a fun story about good vs. evil, and saving the world from destruction.  It would be a good read for 4th graders and up.  The biography at the end gives details about the characters that are not in the story line,  a fun way for kids to see the creative side of writing a character.  The biographies about the author and illustrator are also written in a way kids would enjoy.  This is a good book for looking at how people with different views can work together to accomplish an end all will be happy with .