Definition of Dramatic Irony
One of the novel's most poignant uses of dramatic irony is Oskar's relationship with "the renter," a mute older man who moves into his grandmother's apartment. To Oskar, the renter is a stranger with whom he can share his story. What Oskar doesn't realize, and what the reader comes to know, is that the renter is actually his grandfather, Thomas Schell Sr., who abandoned the family decades earlier.
This irony sharpens the emotional stakes of their conversations. When Oskar confides in the renter about his grief, he is unknowingly speaking to his father's father. The reader sees the generational echoes of Dresden and 9/11 colliding in one apartment. That overlap gives their exchanges an added weight that Oskar himself cannot yet feel.
Late in the novel, Oskar narrates the exhumation of his father's grave and says:
I don't think I figured out that he was my grandpa, not even in the deep parts of my brain. I definitely didn't make the connection between the letters in his suitcase and the envelopes in Grandma's dresser, even if I should have.
But I must have understood something, I must have, because why else would I have opened my left hand?
Here, Oskar reveals an unconscious recognition that passes between himself and his grandfather. Foer leaves space for the possibility that grief can connect people in ways that bypass deliberate knowledge and that some truths are felt before they are known.