Oh, how I read in childhood! I too was a very precocious reader, and I vividly remember one of the first adult books that I read was Stone's The Agony and the Ecstasy about Michelanglo. Another early one was Massie's biography of Nicholas II and Alexandra.
I adored the Black Stallion books, Lloyd Alexander's Prydain novels, Madeline L'Engle's Time novels, I wore out a set of the Anne of Green Gables series and the Little House books -- The Long Winter is still one of my favourites. Charlotte's Web, the Arthur Lang Coloured Fairy books, The Egypt Game, Mistress of the Two Lands (I was an Egypt nut back then), and many others that I can't remember.
But one thing that I do remember was that nothing was forbidden to me to read, and devour books I did. Oddly, my brother never turned into a reader, and my mother only read if a book was needed for her work, or if it was fashionable to have it on her shelves. So I have no idea where I got my need for books from.