It's absolute studio malpractice that this movie got dumped into theaters with hardly any promotion. It's an instant classic and should be a decent sized hit!
Yes, it's a "serial killer" movie, bloody but not gory and it does a fantastic job of inverting your expectations - a truly fresh take on fairly stale genre. At the risk of spoiling some great twists, I will say no more. If you like intense thrillers, just go and see it with as little foreknowledge as you can. Vibe-wise, the review likening it to Tarantino mixed with (good) M. Night Shyamalan is spot on.