I was always a bit ahead of my age reading wise. Startled a teacher in grade 7 (I think it was 7 and not 8 based on which teacher it was) by reading H. G. Wells at that age (I bought a set of four of his novels to read on a trip). The War of the Worlds remains one of my all time favourite novels. Several other all time favourites followed in grade 8, like The Lord of the Rings and Dracula.
But younger than that, I don't recall a lot of specifics. I think I was already reading a lot of non-fiction (somewhat under the influence of a great aunt who was a retired teacher). There was a series called How & Why Wonder Books that helped engage my still ongoing interest in science. The ones on Dinosaurs and Atomic Energy were especially influential and had I gone into the sciences, it would have been either paleontology or physics. I think I started reading those while still in elementary school.
Where the Wild Things Are by Maurice Sendak is one I recall enjoying. I was fond of Dr. Seuss, I think (I still love poetry today). I know I read some abridged classics as early as grade 5 or 6. Stuff like Verne's Twenty Thousand Leagues Under the Sea (admittedly, I probably read that one because I was a fan of the Disney movie version starring Kirk Douglas and James Mason). I think I first encountered Roald Dahl through a teacher reading the Charlie books to the class somewhere in the grade 5-6 range and then later got and read them myself (I loved Great Glass Elevator, actually).
In the end, I became an avid reader for many years but have some kind of weird block right now that makes it hard for me to get very far in novels anymore, even as I write fiction of my own.