Great watch, would watch again, and can recommend.
It is found footage in the catacombs of France so in addition to shaky cam and odd angles, it does feel really claustrophobic at points. If you were okay with "The Descent", then you're likely fine.
This is based off of a real thing that people do, exploring existing structures, some lost through history, others unused, and even more that are assumed inaccessible from the the layman.
Personally, instead of making these places a crime, people should be able to add infrastructure as needed, but it is the primer for the events of the actual movie. Chased down into the catacombs, they basically just keep going towards insanity.
There are so many good points in the psychological horror of it all, and the great unknown of the caves plus random acts of terror makes a great formula for the events of this movie.
Probably the best "philosopher's stone" story I've ever seen.