What is an example of allusion in the novel, You?

The author alludes to The Da Vinci Code in Italian to symbolize the relationship that Joe wants for himself and Beck. Beck gives him this novel as a gift for saving her life. Later, when Joe has Beck in the cage, he has her read a copy of the Da Vinci Code with him. He believes they will be able to spark a relationship with this shared experience. Instead, Joe realizes after he has killed Beck that she did not even read the whole book when he looked through her copy and saw that Beck had not turned some pages.