Having had several close family members go through significant mental decline, I can honestly say that this movie more accurately depicts what it's like for the caretakers and for the victims of a harsh reality better than any other movie or show I've seen.
Anthony Hopkins is truly amazing as once-strong man whose memories are becoming hopelessly jumbled, trying to keep himself together at times, while others defiantly proclaiming that he's as fine as he ever was and everyone else is out to confuse him for some nefarious purpose. You feel angry with him, hopeless for him, and know that there's nothing that can be done to give the movie a happy ending. And it doesn't shy away from that bleak certainty at all.
Olivia Colman and Olivia Williams are both astounding. The use of both actresses to portray his daughter Anna (and in Williams' case, other characters as well) just adds to the visual language of the film in conveying how confusing and bewildering reality can be for someone losing their relationship with it.
Be prepared going into this. It is brutal. It is honest. It is heartbreaking. It is something that anyone should see to prepare for this kind of thing if it's at all a possibility in a loved one's future.
It's not an easy watch at all, but it's important, brilliant, and truly real.