The Expanse series is a science fiction series written by James S.A. Corey (a pen name for authors Daniel Abraham and Ty Franck). It is set in a future where humanity has colonized the solar system and is on the brink of war between Earth, Mars, and the Belt. The story follows a diverse cast of characters, including a detective, a spaceship captain, and a politician, as they navigate political intrigue, interplanetary conflict, and the discovery of a mysterious alien protomolecule. The Expanse series is known for its complex world-building, realistic depiction of space travel, and compelling characters.