Roadside Picnic (1972)

No saucer ever lands and no alien ever appears on the page. The Strugatsky brothers imagine an extraterrestrial civilization that briefly "visits" Earth, dumps incomprehensible anomalies and artifacts at six sites, and then leaves without ever acknowledging the life around it^[1]. The title carries the whole idea: the visitors were like travelers who pulled over for a roadside picnic and drove on, while humanity is the woodland vermin later picking through their litter. Its "stalkers" risk death slipping into the radioactively lethal "Zone" to loot artifacts for resale. The book flips the usual UFO fantasy — that we are the center of cosmic attention — into something colder: maybe we simply don't matter.