I didn't like Theo, the main character and psychiatrist who's trying to figure out why Alice isn't talking. Two things bothered me: I don't like when a male protagonist comes in convinced he's going to save the poor, helpless female. I also don't like when people knowingly just start leaping over lines, doing things they know are wrong, without a buildup to convince me it's necessary (or at least understandable). Theo was just obsessed with Alice from the get go and thought he could save her, willing to go to any lengths necessary. Sometimes I'm ok with unlikeable characters, but this time it didn't work for me.
The twist at the end was crazy and I did not see it coming (even though I spent most of the book thinking I had), so the book gets a half star bump for it. In hindsight, some of Theo's actions make more sense, but that doesn't mean I liked reading his POV.