Following the craze revived by "The Blair Witch Project" (it had been done before with movies like "Cannibal Holocaust" and "The Last Broadcast"), "Apollo 18" presents itself as footage of NASA's "last" voyage to the moon in the 1970s, showing us the "real" reason why we never went back. Through said footage, we follow the exploits of three American astronauts - two on the lunar surface and one in orbit above the moon - as they discover that the moon is hiding a terribly dark secret. Apparently, there's something already there which has nothing to do with either the Americans or the Russians, and it doesn't want us there... or maybe it does, but for unpleasant reasons. This is not a spoiler, by the way; the trailer reveals as much.
The pros of this movie include, first and foremost, that it's a rather unique idea for a story. Ever since man has first walked on the moon, there really has been no speculation of whether or not the moon supported life (and no, I still believe it doesn't), and ever since Apollo 17, there has been speculation on why we never returned (though it likely has more to do with time, money, and risk than anything else). Another pro is the film's realistic look; the lunar landscape appears realistic, and the special effects are convincing as well. As for the scares, they're plentiful without being overly so.
"Apollo 18" is not without its flaws, though. One thing that had me scratching my head is the high amount of gravity which was shown inside the lunar landing vessel. Contrary to popular belief, there IS gravity on the moon as well as between any two forms of mass, though it's not nearly as strong as what we would find on Earth. You can see the astronauts jumping at large distances while walking on the lunar surface, but not inside the lander. Secondly, I kind of wish they had developed the lunarian creatures a little more. The filmmakers use creative camera work to keep several things hidden, which does help add to the suspense, but I still think it would have helped things more to show the lunarians a little more. In spite of these flaws, the film kept my interest.
I see a lot of people hating this movie. While they have every right to, I'm kind of lost as to a reason why. No, "Apollo 18" isn't a great film, but it's not terrible, either. Just take it for what it is.