Science Bowl

My son gets into the Science Bowl team in his school, which is very surprising to me. He had not read any books additional to his school textbook, and I don't think he even spent much time on his own textbook.
He is in middle-school now and typically only 8th graders make the team.

I know there are so many super-parents with super-kids in this forum. Are there any books/web sites/tutoring he can use?