Here are some of mine (no way to list them all...)
Bobbsey Twins (starting about age 5, until I got bored with the formula, about 7 books in. They put me off formula kids' books for years...except, as below, two particular horse series.)
Marguerite Henry's horse books, most of them. Over and over. I got Misty of Chincoteague for Christmas when I was six and had finished it by that night. Black Stallion and Island Stallion books, also over and over (esp, the first Black Stallion book, clearly the best.) Every horse and dog book I could find in our local library. I particularly loved Terhune's Sunnybank books. I hated The Red Pony, and for a long time found Eric Knight's books (Lassie, Come Home and Bob, Son of Battle) unattractive--it helps to be older and understand the human part of the story. Not all horse and dog stories were written for children or are appropriate for them.)
In addition to books, I read a lot of magazine fiction--The Saturday Evening Post, Colliers, Ladies' Home Journal, and others were always around--some my mother took, some friends of hers took, and magazines were freely traded around. They all had fiction (lots of it) back then, and we kids heard adults discussing their favorites.
My mother took Readers' Digest Condensed Books, and I started reading them at age 8, avoiding the ones that were boring (grownup business and love affairs) but enjoying those having to do with airplanes, technology, politics. Thus I really liked Nevil Shute's The Rainbow and the Rose, A Town Called Alice, and Trustee from the Toolroom. As I got older, I read the relatively few novels and short story collections she owned--which included historical novels and some "romances" of a very old type: Anthony Adverse kept me busy all one summer, and The Rosary (incredibly sentimental but a fine book for a fourteen-year-old girl). gave me an undying passion for English country houses. She also had paperback mysteries--Agatha Christie, mostly, but also some Nero Wolfes. While in junior high I fell into a treasure trove--an old lady with a rental house, who had become my friend because I'd stop and talk to her on the way to and from school, gave me boxes of books, many of them classics.
I was also reading a lot of nonfiction, mostly history (and most of that military history). I loved spy stories, escape stories--real or fictional--and was fascinated by anything to do with aviation or space. But I also loved travel adventure books...hence The Royal Road to Romance (for those who don't know it, nothing to do with relationships, but a partly fictional account of a young man's travels in the East.) I used to spend my lunch money on paperbacks, in high school...still on my shelves are a few of those. I didn't read SF until ninth grade; after gobbling up every bit of it in the school and public libraries, I had to start buying it. Some of my favorite non-SF fiction in this period was by Helen MacInnes (spy adventure), Elizabeth Goudge (fairly complex relationship stories set in England), Mary Stewart (adventure/romance), Leon Uris, Ian Fleming, and Allen Drury. Somewhere I have my reading list for my senior year of high school...that included, in addition to SF and mystery and spy stories, Lawrence Durrell's The Alexandria Quartet (of which I understood very little at that age, being a very naive 17-18, but the language is gorgeous and I did understand that.) I also read, on my own, a lot of Greek literature in translation, starting with a book on mythology I'd been given very early.
A note on literary sensitivity: I was horse crazy and read every book about horses I could get hold of. But the one I remembered for years, without remembering its author, was The Maltese Cat...by Kipling, of course. As soon as I re-found it, and learned who wrote it, I went on a Kipling binge that lasted for years.