Let me start off by saying I am not a Christian (I DO believe in God but I'm afraid that doesn't make me a Christian) - and to answer your question: YES, this is a *Christian* movie, with a very clear message, but I won't spoil the plot for you.
The story in a nutshell is the awakening of a Welsh community in early America, coming to terms with their dark history, seen through the eyes of a ten year old child.
There are flaws. It's based on a novel, so the director had to make difficult choices to narrow down the plot for screen time. The editing wasn't good and led to some incoherency and superficial plot holes. The story sometimes wasn't going anywhere, and the 'horror' scenes best could've been left out, they seem out of place. Special effects looked cheap. Last and least: the accents. They should've invested a bit more in accent training because this sounded like a far fetched (teethless) dialect..
But there's some good performances to be admired. First of all, I tip my hat for Liana Liberato. What a great actress at such a young age. Secondly Soren Fulton did a great job and there was lots of chemistry between him and Liana. And what about Louise Fletcher?! Excellent. The actress who once played the horrid nurse Pratched (One Flew Over the Cuckoo's Nest).. she performed wonderfully and was brilliantly cast.
So let's see what we have here. If you take all these things into account and you're not scared off by evangelism - not bad for a Sunday afternoon.