Very little to share here as far as potentially concerning content.
First, while it is very much made with its children audience in mind, the very youngest and most sensitive readers might not be ready for it, something you may not realize from its very short length (worth skimming through if this may be a concern for your reader).
There are a couple mentions of comic books in a somewhat positive light, which are in a state we Christians almost surely don’t want to encourage our kids towards.
Book mentions that the young boy’s mom passed away in a car accident, which may frighten some readers.
Main character tries to fake sick to avoid a bully (doesn’t work). The idea of skipping school is mentioned once.
The principal of a Christian school is portrayed as a not very good guy
