I was a struggling reader until the 3rd grade.
All of a sudden it clicked and my abilities exploded. I went from reading toad and frog to Lord of the Rings in a year.
I read every book in my 3rd grade classroom and moved on to the school library.
I pledged to myself that I'll buy her any book she asks for. My mom looked down on some of the sci-fi fantasy stuff I wanted as a kid, things that I was burning to read, I don't think it would have done me any harm.
I've tried to keep some odd ball stuff she doesn't know she wants to read around, stuff that delighted me as a kid. Greek mythology, illustrated atlas's, Cool kids science books and what not. I don't think it's easy to guide a kids interest but dangling stuff in front of them and seeing what they bite at seems to be working.