Surprisingly good movie. Not perfect, but I'm giving it 5 stars anyway. The characters and their development are nearly flawless, and that's not something many movies get right, especially not horror/thrillers. I would recommend focusing on the characters when you watch; notice their relationships with each other, their virtues and their flaws.
The plot is nothing spectacular. Not a very satisfying delivery of Lovecraft's Cthulhu. Not a lot of lore was provided though I believe that was intentional.
I recognize that social value does not make a movie good, but one thing I couldn't help loving was that this movie was an unexpected feminist gem. Kristin Steward delivered a powerful, believable role with absolutely no discussion about the fact that she's female. Frankly, this was a better feminist movie than Wonder Woman by 20,000 leagues.
Looking for something to watch? Just watch it.