“The Road Not Taken” is a science fiction short story by American writer Harry Turtledove, set in 2039, in which he presents a fictitious account of a first encounter between humanity and an alien race, the Roxolani.
Recommended by Ben
It’s a first contact story that suggests most species in the galaxy develop an anti-gravity/ftl technology incredibly early, and so they end up colonizing the stars without ever developing beyond 15th century tech