A very unique and fresh premise. Natalie Portman has shown amazing skills, Jon Hamm brings a crisp mature take and the direction and cinematography are tasteful.
I think the reason it got so many negative reviews was that people might not have put themselves in the shoes of a person who after an event that big was losing her sense of self.
The details might have been more appealing like the sexual trepidation, maybe the ending too and definitely her haircut.
But if you truly absorb it, it's a wonderful movie with so many curt hidden masterful meanings. Especially keep going back for Jon Hamm's porch dialogue.