Sounds very similar to what I was doing at her age. I turned out just fine, and looking back, can't imagine that any kind of professional intervention would have gone well. But that's me.

Disagreeing with commenters and the part of the answer, I believe you are correct to wonder about what is driving your daughter to read so voraciously. I also want to commend you for the honesty in your self-appraisal. I'm a bit unsettled about this, and want to give this more thought and do some research; I'll post an answer in the next day or two.

@Arno - Or to Anyone: How do you know that you're just fine? I'm not being sarcastic or intentionally belittling; it's a serious question. Most people would think me/my kids are just fine, and by nearly every parameter in our society, we are quite successful. But I would never say that I'm "just fine" or that my kids are "just fine". My ex has NPD (dx'd by a psychiatrist, not by me), but he thinks he's a great person, and just fine; he truly believes that. The OP deserves more credit.

In that 8-10 age range I was very similar to your daughter, even reading (unrelated) books in class instead of paying attention to the teacher. Two things to consider from my own experience: One is that she might be notably nearsighted and/or her glasses aren't strong enough. If you can't see things at a distance clearly, reading something near your face is much more appealing. The other is Asperger syndrome - in that case, you don't necessarily need to seek professional help, just be aware of the mental strengths and weaknesses that go along with it and help her learn to cope with the latter.

I read a lot as a child. I was just curious, and I didn't especially like the company of other kids because they were too childish. People in the books were doing all kinds of awesome things that are forbidden to people in my social class. Maybe you could look into what she's reading and see what's interesting to her.

The summer I was 9, (in 1961) I read my way through most of the novels of Charles Dickens, and started on HG Wells. My mother was worried enough to take me to the doctor. He questioned me about Great Expectations and seemed satisfied by my answers. My mother asked him if reading 'all those books' would damage my eyes. He said 'Not if he has a good light'.

Congratulations. She's going to be smart and likely a high achiever.

I haven't covered this is my answer, but is there any evidence she's simply tired? To a good reader, reading is restful (unless challenging) and she sounds pretty busy. If she's going through a growth spurt (again, any hints like increased appetite or actual growth?) that could tire her out as well.

@anongoodnurse I know I’m fine. Successful in business, a confident public speaker, I sit on a couple of boards, I advise government, and I help set syllabus for schools and universities. Reading copiously and early sets you up to be able to consume information quickly and completely.