Cap't Underpants- Pilkey 3-4th grade level- the cap't underpants is a little cheeky (no pun intended), they are about the misadventures of two boy who like to play pranks. They hypomtise there principal and he becomes cap't underpants and bad guys show up and the two boys, with the help of cap't underpants somehow always save the day.

Ricky Ricotta- Pilkey 2-3rd grade level A boy mouse and his robot fight bad guys and always save the day, usually learn a lesson.

There are about 9 books in each series.... they are pretty cheep, they have them at target.

DS7 Loved both of those at that age.