Lightning Thief (and sequels) by Rick Riordan

I really liked this series (5 books total). It is funny-Percy is a real smart alec. It is clever- things like Medusa (who turns people to stone) runs a shop selling garden statues. Percy's comments are kind of like the sense of humor you get from Spiderman. You also pick up a useful amount of Greek mythology, which really comes in handy because there are so many allusions to it in our literature and culture. 9th grade English also contains a big mythology component and you will be ready and have fun doing it!