Great watch, could watch again, and can recommend.
Keri Russell does quality crazy lady, and this movie is basically what "Paranormal Activity" should have been combined with a good version of a Slenderman movie.
There's a very satisfying conspiracy meat to the plot: the escalating defenses combined with a literally conspiracy theory "nut".
Part of the fun of this is that it is all presented in a very real, believable manner. The atmosphere the movie creates is reason enough to watch it.