According to today’s Writer's Almanac, George Orwell’s Animal House was turned down by countless London publishers. Finally, a small publisher took it, and Orwell became famous when the book came out in 1945.
I reread Animal Farm a couple years ago, curious to see if it still held up: yes. Tight and compact, while saying so much. (I still retain the image of the pigs turning into horrible, garish, laughing farmers at the end of a cartoon movie we watched in junior high.)