I am a fan of Elena Ferrante. After watching the film, I felt totally dissatisfied - that's not the Elena Ferrante I am familiar with. The movie adaptation has failed to carry out the true spirit of any Elena's original writing.
So I went on to read the original novella (audiobook). I discovered that the film has unwittingly eliminated lots of good subplots including her childhood and friendships, and most importantly, her actual relationships with her daughters. They are so critical to explain the strange behaviors of the protagonist, as well as to make her look less like a bad mother but more of a struggling young woman with hopes and dreams.
No doubt the plot by itself seems weak and baffling. In the book, the author (in her signature writing style) has brutally yet poignantly depicted all the complicated emotional struggles and introspective impulses of a working mother throughout her youth and midlife. As usual, it is a very cathartic experience and I absolutely enjoy the book regardless of her dissatisfying ending. But the film seems to miss all those critical elements, including lots of quotable and meaningful monologues and dialogues that make the plot more palatable and decipherable. All we see in the film is a sad middle-aged woman vacationing alone with no purpose and meaningful conversation.
I think Elena's intention is for the readers to understand and emphasize the protagonist's struggles with no judgement. Unfortunately the film seems to mislead the audience to an opposite direction.
Sometimes a movie is better adapted than the original work, consider "The Handmaid's Tale - Season 1. But "The lost Daughter" is a huge disappointment, especially if you have already watched HBO's "The Brilliant Friend", an Italian production.
I have no idea whom the lost daughter is and what ending is supposed to mean until I have finished reading/listening to the audiobook. The latter is so much more compelling than the slow-burn movie adaptation lacking in depth and meaning.