It's impossible to discuss Moon without dropping a few spoilers. Even if you only watch the trailer, you'll learn of the first--of many--twists in the movie: There's apparently more than one version of Sam Rockwell's character on the moon. You learn this like thirty minutes into the movie and though it's a surprise, within the first five minutes of the movie, director Duncan Jones goes out of his way to make it very obvious Moon is full of twists and unexpected shifts in tone and sensibility.
This isn't lead-footed, clunky storytelling though, it's no bullshit, really honest storytelling. Rather than send you on a contrived twisty-turny series of narrative flips and dead-ends, Jones comes out and establishes the unreliability of "facts" right away. This is something all the more in demand given the pervasive, trust-no-one cynicism and "trick-ending" obsessions of movies as of late.
Sam, an astronaut on a three-year project to harvest H3 from the sun (or something) that then gets sent to earth is not-well from the first moments we see him. Though he's charming and self-aware about his isolation, there's a terrifying edge to it. It's almost like Rockwell's character from David Gordon Green's Snow Angels was sent on a space mission.
He's first shown hallucinating a woman sitting in his recliner--the movie's full of human/humane details like Sam having a recliner on the ship, or wearing slippers and trackpants, or listening to Katrina & the Waves--and a few moments later, transmissions from earth seem jagged and incomplete or malfunctioning. His HAL-like computer, Gerty, simply by being in the movie and playing off of HAL-9000, gives us a kind of knowing "this'll end weird" feeling. As I said, this helps the ever-shifting reality of the Sam character go down much easier: Stuff's screwy from the start. The rug's being tugged from minute one, so when it gets pulled from under your thirty minutes later, you were totally warned. It's less about twists and more about surrounding the twists in characterization and emotion so that when they happen, they mean something.
Without leading you on how the movie gets there, it becomes clear really early that Sam's a clone and that the other Sam is a clone too and that the company, a private company--a very important detail--that's harvesting H3 for the good of the earth is involved in some fairly questionable practices.
This makes the movie quinessentially 2009, despite its clear devotion to Sci-fi of the 70s--especially Silent Running. It's 2009, and we're no longer mindless consumers and wasters, nor are we enlightened, guilt-ridden conservationists, we're all kind of these environmental, earthly, ironists. "Green" is a political/social stance, but it's also tagline and stream of products. We're all well aware of our carbon footprints, doing something or other to curb it, but not enough, and we're sure to take note when we're wasting or abusing mother earth. Moon confronts you with the negatives of our luxuries.
Our irony towards the use and abuse of resources isn't necessarily a bad thing (it's honest at least), but it leads to a strange, knee-jerk self-justification when we buy something at Wal-Mart or throw out that IKEA dresser because it's easier to just buy a new one for 40 bucks than lug it up the stairs of our next apartment. What Moon does is wrestle with the "break some eggs to make an omelet" debate we all have in regards to living in a convenient Western world without falling on self-justification or self-righteousness. Here the "Eggs" are clones of an original Sam tricked to thinking they have a fully-functioning life and then having it ripped away from them under the guise of a "return" home--a home they only possess via implanted memories.
If it's solved the energy crisis, does it matter that some clones suffer some crucial emotional breakdowns? Jones doesn't even wrestle with that question though or rather, he wrestles with it by taking the characters seriously and simply dropping us into their existential dilemma; he doesn't allegorize or symbolize it. It feels rarefied and specific.
Unlike the past however many years of Sci-fi which likes to think "What makes us human?" is actually a fascinating question, Moon humanizes everybody--even a clunky, emoticon communicating robot--and lets the actual human and not-so-human drama play out. Moon grabs us via emotion and not ethical pondering. We're stuck on a spaceship with the eggs to be broken and it's all we ever really get to see, and so we don't even consider the omelet anymore.
And that's the brilliance of Moon, the big picture becomes implicit and the tiny little emotions at-hand takeover. Science-fiction often gets bogged down in explanation, exposition, or just a shit-ton of throat-clearing and so, a movie that just keeps it moving, that's focused on contingency and not definites (be them world-building or ethical) is a delight.