Very funny. Definitely more immature and indecent in comparison to the Captain Underpants books (a character is literally turned into a piece of poop), but funny nonetheless. Silly and entertaining.
The story is much simpler than the Captain Underpants books as well. This is because it is written entirely in comic format. The story fully takes place in George and Harold's imaginations instead of bouncing between reality and "fiction".
Still a good read. I enjoyed it. A great quick read.