The movie is at times a bit slow, and the actress' acting a bit flat but that is part of the whole intriguing plot, which as you suspected at the beginning, is true.
If you're hoping to see porn in the movie just because the descriptions seem to want to tell you that the woman is a porn addict, think differently. The only skin that you'll see is her naked back a few times.
Although the plot unfolds very slowly, that's the point. There are some mental health and abuse issues here, and in real-time most similar interactions would never progress as far as this movie does by the end, and most likely far less successfully as the eventual turnout of the plot.
Interesting, intriguing, not Oscar-candidate but a strong entry especially considering the topic(s) involved.