Lights Out
Thoughts
Most horror movies are fun when they let you fear the unknown. Lights Out has an almost videogame-like approach that's the opposite of this, but it's highly entertaining. It has structure and a set of rules that make the fear a little more real. You know when a person is safe and when shit's fucked, and light is such a dynamic element that you can do lots of interesting set-pieces with it and not have it get stale. It's a simple concept, but effective.
The narrative conceit is good too. The strain that the main character feels with her family, particularly her mom's mental illness, is all too realistic, and it gels well with the magical monster shit. It's a good movie imo! At least as far as horror goes.