Extraordinarily well executed, fresh, replete with lots of smart details bring it all to life. The characters are believable; raw and wild, running on their baser instincts, struggling to be civil in a world where gnash-toothed animals survive and civility only gets you dead. They try to be civil! Oh bless their hearts they try.
What I loved the most is the transformation you see in the characters; they go from feral, viciously unlikeable creeps to slowly warming up and right before your eyes they bloom into something like humans again, full of love and empathy and hate and greed and loyalty and all the paradoxes of the human condition. The setting is well fleshed out, with enough mystery regarding the details of society's breakdown to suspend any disbelief you might have about the premise. You feel like it's real. The characters further help you sense the desperation and anxiety of the world portrayed here. It's very somatic; you feel the hunger, the distrust, the anger and the violence of revenge.
I was left feeling grateful for the world I live in, which is the purpose of theme I suspect. It really could be worse. Watch this movie and feel intense gratitude for your humdrum life. Enjoy!