When someone grows nostalgic about childhood books, they generally talk about fiction, but my fiction reading nearly all came from the library and had to go back, so I don’t remember it as clearly as the nonfiction in the bookcase that I’d flip through and look at the pictures and read some here and there.
I can't remember specific titles but Usbourne books did tonnes of non fiction books on history, space and how the body works that I loved.
But the Horrible Histories series probably won hands down.