How does the epistolary format of this novel affect the story’s plot?

The epistolary format allows the tale to unfold through letters, notes and telegrams, which lends a reflective air to the action. As a result, the story unfolds so naturally that it communicates key plots points well in advance, and the characters, even while recounting tragic events, are able to convey their stories all while remaining positive and without a display of angst or fear.