Books for 12 year old boy

My family have recently taken guardianship of my 12 year old cousin.
Previously to being uplifted, he was forced not to go to school for a while so his reading , writing & numeracy is well below average.
He can’t wait to get back to school which is great news.
We bought him Artemis Fowl recently , he is on his 2nd book.
What other books along the same lines, for a boy & not too difficult to read could I find for him to pass the time ?

It can’t be too sad or to do with drugs, mental illness, broken families or abuse.
My thoughts were maybe fantasy to take his mind off things or even something with some comedy to make him smile.

Thank you

by llama_farmer00