Follow the lead of the child would be my suggestion, and nurture their interest in books in whatever way works for them. I would let my kids read whatever *they* want although I discourage content with a *mature theme.* I have an 11 yo dd with an almost insatiable appetite for the written word, and has since she was a baby. She knows what she likes, and us parents consider our job to be maintaining the flow of books. She thinks nothing of reading two 300 page books in a day, so we're talking high volume, and we use the library extensively to keep costs down. We cater mostly to her interests in selecting books (we leave it to the school to force her to sample other genres - that's why we send her!), as we think her love and skill in reading is one of her greatest gifts and want to nurture it. For science/math, "Murderous Maths" and "Horrible Science" series have been favorites for years (we own these ones) and she rereads them periodically - I think she rereads because she likes the humor, and also because she comprehends more each time. She also enjoys some books well below her reading level (she read a Goosebumps book the other day) and we indulge that as well, and always have.
