If Charlie is a better auditory learner, you may also want to consider getting it on tape/cd or reading the book with/to him and use that in conjunction with a study guide. If you listen/read it with him, you may also be able stop at points and ask some relevant questions from the study guide.

Scholastic reading guide: http://www.scholastic.com/kids/homework/pdfs/Roll_of_Thunder.pdf

http://www.patinsproject.com/universal_design_for_learning_project_files/avon_lesson2.pdf

http://www.bookrags.com/notes/roth/

leslie