CONTAINS NO SPOILERS, BECAUSE THAT WOULD SPOIL IT
Here's a confession that in a sane world would see me burned as a heretic: I've a lot of time for M Night Shyamalan. I think he has good ideas, and I think he directs well and with subtlety (I'm all in favour of a director who nails the camera to the floor and lets a take run for 30 seconds rather than flinging the camera all around the room and micro-editing everything into an epileptic frenzy). My problem, and my frustration, is that I don't think he's very good at the middle bit of the process, which is taking those ideas and building a really decent script out of them; so you end up with a well made film from a shaky screenplay. And his first two big movies (The Sixth Sense and Unbreakable) were terrific, even though some gurning web-based buffoon deliberately, and with malice aforethought, spoiled the twist from The Sixth Sense a few days before I saw it.
And I liked Signs, even though it's nonsense (if the aliens are so scared of water, why do they land on a planet which is 60% covered in the stuff and where it rains all the time?). The Village has some very scary moments with the red creatures in the woods, but it depends on none of the village elders ever saying "sod this for a game of soldiers, I want a cheeseburger". I did like The Happening, where the funniest bit is Mark Wahlberg calling a truce with a rubber plant. Then you have Lady In The Water, which I'm the only person on Earth to not loathe: does no-one else realise that it's a kids' movie? And The Last Airbender (in 2D) is acceptable enough CGI-laden matinee fodder with too many sniggersome uses of the word "bender" in the screenplay.
But all he's done with Devil is supply the original idea (and possibly the overarching concept of The Night Chronicles, of which this is apparently the first). In practice it's the simplest back-of-a-fag-packet setup in years: There are five people in a lift and one of them might be Satan. That's it. And from that, they're extracted a perfectly serviceable, acceptable, mid-range horror movie that does the job efficiently and with a minimum of fuss and overblown effects, although the religious-minded security guard is far too convenient to be believed. It's directed by John Erick Dowdle, who "directed" Quarantine, the American remake of [Rec], though whether he actually "directed" it, given that every directorial decision had already been taken by Jaume Balaguero and Paco Plaza in the Spanish original, is perhaps open to question.
In places it actually feels a bit like the great-yet-flawed Prince Of Darkness (my second favourite John Carpenter movie despite some awful writing and worse acting), and while Devil is nowhere in that league, it's generally entertaining fare and very nicely shot, with an old-fashioned orchestral score. Shyamalan perhaps needs to redeem himself in the eyes of many, both the critics and the general public, and his involvement here, and presumably any forthcoming Night Chronicles instalments (though none are listed on the IMDb) might do that. Worth seeing.