Address Unknown is an epistolary novel, meaning that it is structured and presented as a series of letters or telegrams. As such, the letters, addresses, and stationery used throughout the story become important symbols. Even though Martin and Max are on different continents, their letters suggest an initial desire to maintain their friendship. Max’s early letters to Martin are warm and friendly, reflecting his apparent affection for his friend.

As Martin becomes radicalized by the Nazi party, however, the frequency of the letters changes. They are less warm, less friendly, and less representative of a desire to stay in touch. By the time Griselle reaches Berlin, Max’s only reason for continuing to write is out of desperation for his sister’s well-being. These letters go unanswered until Martin sends a blunt declaration of Griselle’s death. From then on, the only letters Max sends are those that lead to Martin’s downfall—the purpose of letter-writing shifts from a way to build connection to a means of destruction. The nature and frequency of the letters reflects the collapsing relationship between the two men and portrays the shift in power dynamics over the course of the story.