European (or at least German) cinema isn't exactly known for its genre blockbusters. Most of it are silly comedies or dead-serious dramas, often historical. These usually come across (to me) as pretentious and unauthentic, screaming to be taken seriously while mostly failing at visual storytelling.
This movie seemed to fit right into that category. Surprisingly, it doesn't. While there were some moments in the movie where I thought it was a bit constructed, it felt very honest overall. It takes itself serious, but also its audience and medium. It is real cinema, gripping and atmospheric, but also not over-styled. Desipite it's substance matter it's not a talking-heads movie, but knows when to let the visuals and music talk for themselves.
If you have seen the trailer, you probably already know a bit too much. On the other hand, the movie really isn't about any plot-twists or spectacular effects, and it thankfully avoids those and other clichés completely. It should be noted that it is rather slow-paced, and some plot-points are left open, but that's very likely all deliberate and very fitting. The only real complaint I have is the jarring Apple product placement. That was so out of place I wanted to throw up.
One more thing: Note that the title is "Mercy". Some critics talk about forgiveness in relation to the story, but without spoiling anything, that is precisely NOT what it is about.
