It's also a thinking person's movie. Nothing explodes and no one's head rolls down a staircase and there's no blood and gore, but my oh my, is it a compelling story.
There are a lot of messages you can take away from this movie but the one that rings most true to me is a quote I heard many years ago from William Barclay (Bible scholar). He said that evil seeks to breech our spiritual fortress in our weakest places and in our strongest places and that we should be vigilant to guard those two "low spots." The other reason I loved this movie is it's about "every man" and each plot and sub-plot is very believable and has no discernible plot holes (as so many movies do). It's very well-written, well-acted and deliciously interesting. You may want to watch it twice, to make sure you miss nothing.