What I really liked about this film was the constant use of a found footage style. It's supposed to be a documentary of the experience, and it therefore immerses the viewer in what is going on. This made the film incredibly intense and exciting as you were seeing what the characters saw. This would link in with Blumler and Katz's uses and gratifications theory in the point that the audience want to identify with the characters of the situation.
I also really liked the tension it created with so few "jump scares", instead playing with psychological fears such as claustrophobia and guilt of deaths. However, I felt that the ending wasn't as good as it could have been, relying too much on a supernatural element when it had started off with a more natural style.
I first found out about the film through a promotional YouTube video by Felix Kjellberg (aka PewDiePie). He embarked on a quest through the catacombs with his girlfriend where they were scared in multiple ways, creating an almost real life horror game.