This is a "found footage" film. For anyone who doesn't know that term, think The Blair Witch Project.

The basic story is, and you can see it on IMDB, is that NASA stopped missions to the moon at Apollo 17. Further missions were unknown since they stopped doing them, but a secret DoD mission was made, and that mission was Apollo 18.

As with films of this type they claim the footage was found after such and such an incident.

Uncredited actors/astronauts are sent to the moon in 1974. The tagline is "This is why we never returned to the moon." or some such nonsense.

I think this is the Blair Witch in space. Which could be a spinoff title in it's own right

This movie does build tension, jump scares, flickering cameras, and an unknown antagonist for most of the film. The mystery is what makes this film work. Perhaps it's what District 9 could have been had they kept the same format without changing point-of-view or stylized type of filming. So, in that sense, it was more coherent.

Officially, even now, there was no "Apollo 18". Research on it will show you some interesting information. Perhaps this is why that mission is portrayed here. The simple fact that no one knows.

It's a bit of a period film hinging on the Cold War with the Russians. It is not the basis of this film though, but helps to drive the plot forward as it's time period would naturally suggest.

I'm not the best judge on horror movies. I don't watch a lot of them and I don't know the genre well. This was a suspense/tension/horror film with a Blair Witch sort of resolution.

As much as I've been able to rant, there are better horror movie experts here...