Would Horrible Science/Murderous Math be appropriate? He's maybe too young, right? I've seen them mentioned so many times here, but have stayed away because my kids are not into scary stuff. DS in particular is in a phase where he is very easily freaked out.

Has anyone tried those Magic Schoolbus kits? I was eyeing them. Wasn't sure if they would require too much parental fiddling. He is plowing through those chapter books right now.