Obsession is a major theme in the novel. The protagonist and narrator is a man prone to obsessions, to the point where the narration itself addresses the object of his obsession—hence the novel’s title, You. Joe’s fixation drives him to heinous actions which he then dedicates to Beck. In his mind, he is helping her and improving her life; this shows how his obsessions lead to delusion, breaking him from reality. To Joe, stealing a woman’s phone and using her private emails to stalk her for months is an act of love. His obsession masks reality, and he stalks, hurts, and kills anyone who stands between him and his fantasy. His obsession reduces Beck to an object, turning her from a person into a possession.

However, Joe’s obsession is built on a shifting reality. The obsession develops from the first moment he sees her in his bookstore. He knows nothing about Beck beyond her surface aesthetics: he knows about her clothes, her conversation, and her literary tastes—but this is enough for Joe to become obsessed, and he fills in the gaps of his knowledge with his own desires and assumptions. Beck becomes a blank slate onto which Joe can project his idea of an ideal woman.