Arkady Strugatsky

Red Schuhart is a stalker, one of those young rebels who are compelled to venture illegally into the Zone to collect the mysterious artifacts that the alien visitors left scattered around....

Anton is an undercover operative from future Earth, who travels to an alien world whose culture has not progressed beyond the Middle Ages. Although in possession of far more advanced knowledge than the society around him, he is forbidden to interfere with the natural progress of history....

The Doomed City is set in an experimental city whose sun gets switched on in the morning and off at night, a city bordered by an abyss on one side and an impossibly high wall on the other....