A very well done horror film. One thing I'm always appreciative of is when a movie can work with very few sets, and very few actors.
P2 works with the single setting of a parking garage and 2 characters. There are a couple side people here and there, but for the most part you only have 1 terrifying stalker to keep track of.
The movie does an amazing job at highlighting someone who just doesn't understand what's going wrong with the situation. He continually asks "Why are you doing this?" while his victim tries to escape, clearly not realizing he's in the wrong.
Wonderful time, I heavily recommend it.