Director/writer Duncan Jones' film Moon is a quiet character study which just happens to be set in outer space.
The film centers around Sam (played by Sam Rockwell) an astronaut working on a lunar refinery base for a 3 year stretch. Sam is alone, accompanied only by the base's computer system (creepily voiced by Kevin Spacey). The viewer meets Sam a few weeks before he's scheduled to be picked up and returned home. From the very beginning, it's clear that his time alone on the moon is starting to wear on him. He's getting aggressive, feeling ill, and starting to see things which aren't there. Very soon, Sam is exposed to a revelation which changes the meaning of his entire life.
The central twist of the film occurs very early on and it's therefore nearly impossible to talk about the plot of the film without ruining that twist.
Accompanied by Clint Mansell's haunting score, the viewer is propelled with Sam through a series of events which gradually explain not only his nature, but also the nature of the world in which he lives. But at the film's heart, it is a very particular character study. Jones' plot allows the exploration of Sam's character in a very unique manner and Rockwell makes use of this to deliver a fantastic performance. Kevin Spacey's understated performance goes along well with Rockwell's, making the computer he portrays enigmatic and sympathetic.
Moon is a low budget science fiction joy which uses the best conventions of the genre to explore what human life really means. It's a lofty goal, but Jones and company accomplish it with ease.