"Encouraging them to read anything is a good idea, and if a student latches on to a series or genre they like, be happy about it."

This is precisely what I did with my son. With the obvious exception of porn, I never censored what he read. As a result, he was tested at 12th grade level english skills in the 8th grade. That's the secret, I think. Be happy about it. They're reading and they're enjoying it.