Although people may approach it seeking a horror film, and despite having some paranormal elements to it, the movie is mostly a missing persons mystery. The film weaves two "main" storylines as well as two missing persons cases deftly into a film that culminates into a single picture in the end.
The characters are not really fleshed out more than they have to, which is a good thing, and the actors do a pretty good job bringing the characters to life, especially the psychiatrist.
There weren't much jump scares or purely horror scenes, and what little "scary" scenes did show up added to the atmosphere and mystery, and made sense to the plot and eventual background "mythology" of the movie. As such, this movie should be fine for people who aren't really into horror movies, if they can handle a pinch of supernatural as a part of the mythology instead it being intended purely for horror purposes.
The movie was pretty focused on the main story, and there weren't much side stories or unnecessary relationships, violence, intimate scenes, or anything that really distracted from the story for the sake of sensational viewing. The pacing was slow but steady. To be honest, it was so slow and steady that was almost beginning to suspect that the film would have disappointing ending, due to the relatively nonfluctuating levels of emotion or suspense. However, despite the the ending indeed being technically anticlimactic, I think it was indeed satisfying, resolving the main mysteries while still leaving room for thought and reflection.
I would definitely recommend this movie for anyone who likes mystery, and don't mind a teaspoon of spook in that.