Two Great Books by Poul Anderson: The High Crusade and The Golden Slave
If Three Hearts and Three Lions owes something to A Connecticut Yankee in King Arthur’s Court, then so does The High Crusade. But The High Crusade inverts Mark Twain’s concept. This book isn’t written by a modern who time traveled to Arthur’s court, but rather is written by a medieval scribe who witnessed Sir Roger Baron de Tourneville and his knights and court invade an alien spaceship and end up using it to conquer a major portion of interstellar Space….