Fantastic.

Rating: 9/10 (18 December 2015)

Initially, from my viewing of the initial trailer for the movie, I had felt like this might be a thin, silly metaphor for STDs, but seeing how much more complex and fabulous this movie is, I'm pretty happy to say right here at the start, that you need to get out and see this movie if you're able. Right now.
I have so much to say about this, but I also don't want to get too deep into the story details, so I'll sum of the story elements briefly first, and then get into the rest of things that I loved about this. The story is tense, interesting and, with the exception of a couple of silly "horror moments", kept me guessing and wondering. It really does a great job of balancing the "show don't tell" method that is always effective in horror movies, with some genuinely chilling moments from start to finish.
The movie is shot beautifully, the cinematography drags you in by the face, and forces you to join these characters in the nightmare they are living in. Not only is it incredibly effective at deeply immersing you in the world, but may of the shots are genuinely beautiful, and really work to create a haunting world. There are a lot of moments throughout that leave everything up to your interpretation of how events unfold, and really add some depth to an already hugely engaging movie.
On top of the cinematography, you have probably one of the most oppressive and fantastic soundtracks ever. I immediately thought of movies like Drive, and even some of John Carpenter's soundtracks, terms of effectiveness. Some elements even gave me the same sensation that the final scene of Requiem For A Dream did, and they added so much to the movie. Some of the scenes are unbearably tense, and the soundtrack just pushes you right over the edge.
On top of everything, we have hugely likable characters played by really wonderful actors. There wasn't anyone in this movie who didn't really do a great job. Each actor seemed to fit really well, and it brought that much more to the movie. Everything about the movie felt very intimate, and these characters really worked for me. Maika Monroe (The Guest) is so great, and carries the movie really well. I also found everyone else really likable, and even felt like the characters were written as real people, and not like what movies want male and female characters to be. Hell, one of the female characters casually rips a fart in her introduction and it's laughed off in the same way as it would had it been a male character. It's a little thing, but I really did appreciate it.
There's a lot of small details in this movie that really stood out to me, and made me wonder about the reality of the movie all the way through, it's subtle, and intense, and just so so so so great.
This is easily the best movie I've seen so far this year, and I have a feeling will be making its way on to plenty of top 10 lists when 2016 rolls around. Get out and see it as soon as you can, if you can still see it in theaters, then do it. Stop sorting through the garbage pile of 2015 direct-to-streaming/DVD releases and get on this bandwagon already.