As I stated earlier in the thread, I've been really disappointed in most of these highly praised "horror" films in recent years, but this one clicked for me. Really, really well done and about perfect pacing.
I thought it gave a grim, realistic look at what survival in that situation would be like and gave a perspective from every age and angle. I didn't need it spelled out to me what happened to the world and how/why the families were in that house and that time. All that mattered is both families WERE there and the inevitable tension between them hanging in the air at all times until a boiling point.