This was an amazing movie, to a large extent because of its lead actors. I expected Juliette Binoche and Kristen Stewart to make a great team, and they did; there was never a moment when I thought one of them was out-acting the other, or drawing attention from the other. They worked in perfect tandem as far as I could see.
The first thing that needs to be mentioned is the technique of telling the story in "layers." Many, if not all, scenes are on multiple levels, filled with subtext, and it all mixes effortlessly with the central story.
Binoche plays famous and respected actress Maria Enders, while Kristen plays her devoted personal assistant, Valentine. Enders is preparing to play an important role: the character of Helena, an older woman in a remake of the play in which she once starred brilliantly as the more powerful younger character, Sigrid. Valentine is helping her rehearse, and they both travel to the picturesque mountain town of Sils Maria to work on the play. That's the main "layer" and it makes a perfectly good story on its own. But in this movie, any piece of dialogue can, at the same time, refer to the characters in Enders' play; to Enders and Valentine themselves; to Binoche and Stewart; or to other actors, movies, directors, or events which are not directly mentioned in the film. Yes, even the real life actors are referenced; Olivier Assayas confirmed in an interview that in this movie, the identity of the actual actors is part of the story. It sounds as if it should be weird and confusing, but it's not; it's done very smoothly, with the main story easy to follow even while taking in the other layers of reference as if they were background music.
The basic story, which is beautifully told, is about a woman struggling to deal with ageing in a profession that doesn't always respect older women, that may consider them irrelevant. Maria Enders is also trying to be true to her art while making the necessary concessions to fame, the media, the fans, fellow actors, and critics, concessions she resents to some extent. It would be a fine story all by itself. But the added layers provide a sort of ongoing commentary on the story, that makes it much more interesting, and a little strange. Seeing obvious parallels with the lead actors' real lives is odd, but like the parallels between Maria Enders and the character she is preparing to play, it only adds depth to the story and gives us more insight into what is happening.
Maria's struggle is made worse when she meets the young, brash, gossip-ridden Hollywood actress, Joanne Ellis (Chloe Grace Moretz), who is to take on the role of Sigrid. Joanne is smart, fearless, and media-savvy. At their first meeting she flatters Maria and claims to be an admirer, but may simply be feigning respect. Maria is easy to sympathize with when she looks into Joanne's background and sees that the rising star displacing her is a crude, grandstanding girl who manipulates the system to her advantage, and who acts in ridiculous sci-fi drivel.
Gradually, the difficult relationship between the characters in Enders' play becomes blurred and overlapped with Enders' relationship with Valentine, each relationship providing commentary on the other. It is interesting to watch Binoche simultaneously rehearsing a scene in which her character, Helena, has a confrontation with Sigrid, and in subtext confronting Valentine. It gradually becomes unclear whether she is Helena addressing Sigrid, or Maria addressing Valentine, because it becomes both at once.
Maria's conflicts over becoming obsolete in the field where she's excelled, and by extension possibly in her life, causes ongoing friction with Valentine, who tries to help her and encourage her to change her perspective. Finally, in a brief surreal moment, Maria, it is implied, manages to take on Valentine's perspective and her confidence. As Valentine tries to express at one point, Helena and Sigrid are really the same character; by extension, so are Maria and the young, pragmatic, fearless Valentine. Ultimately these opposites are reconciled, the conflicting layers are brought together, and Maria is able to accept her new reality and move on. It's not necessarily a happy ending, in terms of Maria's diminishing professional range, but it is a satisfying one.
This is an enjoyable, well written and well acted, serious and yet consistently entertaining movie from beginning to end.