Hard to Be a God

A group of 30 scientists travel from Earth to a nearly-identical alien planet that is culturally and technologically centuries behind. The inhabitants of this planet have brutally suppressed a Renaissance movement, murdering anyone they consider an intellectual, and thus the planet is stuck in the Middle Ages. Anton, one of the scientists from Earth, assumes the identity of Don Rumata, a nobleman who resides in a large castle surrounded by poverty, and infiltrates the local populace to help them progress as a society without interfering violently or killing anyone.