You can't get any more knowledgeable in the field of children's literature than Roger Sutton. This is from an article about choosing books for kids in the November/ December issue of Horn Book. Here's Mr. Sutton on helping good readers become passionate about books. And a word or two about parenting while he's at it:
Parents of an early expert reader — heck, parents of any kind of a reader, from reluctant to ambitious — are confronted with two sometimes-conflicting sets of expectations: what they want for their child and what their child wants for him- or herself. I would suggest that, ultimately, satisfaction will be found for the former by assiduous attention to the latter. Just because your child can read at a fifth-grade level doesn’t mean he needs to at all times. (Think about your own reading: just because you can read Henry James doesn’t mean you must, does it?) At the same time, of course, just because your child is seven doesn’t mean she can’t take a crack — if she wants to — at Harry Potter, either. Given access to a wide variety of reading — both print and pixeled texts — and given the proper tools and encouragement to wade through it and choose, children turn themselves into the readers their parents want them to be.