The A.O. Scott review captures it well. I particularly like his phrase: "it is both an impeccably Gallic delicacy and a gleeful parody of Frenchness"
Scott also says: "After it’s over, you may find yourself in an argument about just what kind of movie you saw. A nasty, exploitative spectacle of a woman’s victimization, or the celebration of her resistance? A feminist tale of rape and revenge, or an exercise in chic, cynical misogyny?" In fact, I had exactly this discussion after the movie, and the answer really isn't clear.
Recommended, but not if you are triggered by sexual violence.