I'm truly confused by the really awful reviews of this movie. I get it's not for everyone, but it's actually a pretty good & thought-provoking movie, so it would seem that the concept is being missed by reviewers.
I'll TRY to avoid spoilers, but even the genre is a spoiler so don't read any reviews beforehand for the best experience.
What the movie ISN'T: It is NOT a SciFi movie, & it's NOT an Inception clone.
What the movie IS: A statement that perception isn't reality. And a look at what happens when you hit mental rock bottom. Everything in the movie is up in the air as to whether it's real. One thing to remember is something Salma's character says early on, as it clues you in throughout the rest of the movie. And if you have any questions at the end, I'd refer you to Salma's last scene & Owen's witnessing it before making his decision.
Seriously, if you have an open mind & like a different approach to storytelling, give it a try. It's one of my favorite recent releases.