I came up with this because I learned from Tumblr that there’s apparently more than a hundred fanfics for The Epic of Gilgamesh on Ao3, and I think it’s poetic in a way how we’ve still never really gotten over the first story ever.
My answer would be Le Roman de Silence, from the early 1200s, which is about the adventures Silence, a boy who was born as a girl (that’s the author’s way of describing him)and who eventually becomes a knight. I just stumbled across it randomly but I fell in love with it after reading it the first time, and I think it’s beautiful how something 1000 years old can still be around and not have lost any of it’s capability for arousing our emotions.
Right now I’d say it’s this strange work by a priest in 1600s Germany, Cautio Criminalis by Friedrich Spee von Langenfeld. It’s nonfiction, and basically just a really interesting and convoluted argument against the witch trials that were commonplace at the time. His reasoning is really interesting because it needs to be logically and theologically sound, but also oppose widely accepted and standard church practice, so it’s a bit of a dance to say the least.