I found it horrifying. I am a twin and my sister is violently mentally ill, to the point I am scared of her and in the past have kept where I was living secret to her. I watch stuff about conjoined twins and I thank the universe we aren't. I watch this and it scared me! BUT, the movie isn't horror, just my unique situation causes me to think that way. A lot of people are calling it science fiction, when it is more fantasy, because it doesn't give scientific -ish reasons and explanations, just starts off as this is how it is. It has interesting concepts, and shows some of the same issues we grew up with, like people treating us as interchangeable when we are very different, and how 2 people can have 100% same genetics and upbringing but be mentally and emotionally very different.