First, the narrator is annoying, and I'm unsure if it's the narrator's voice or the narrator telling the story in the book (the character). So, there's that.

Additionally, I hated the flow of this book, which is like an anthology told through the narrator's different patient files. I couldn't make sense of its relevance. 

Finally, we're supposed to say, "Wow, oh, what a twist." It just didn't cut it for me, but I will say I found it fairly amusing, so I'll give it points for that.