Roadside Picnic by Arkady and Boris Strugatsky.

Roadside Picnic (Russian: Пикник на обочине, romanized: Piknik na obochine, IPA: [pʲɪkˈnʲik nɐ ɐˈbot͡ɕɪnʲe]) is a philosophical science fiction novel by the Soviet authors Arkady and Boris Strugatsky. It was written in 1971 and published in 1972, and is their most popular and most widely translated novel outside the former Soviet Union. As of 2003, Boris Strugatsky counted 55 publications of Roadside Picnic in 22 countries.