Age of Iron is a great example of an epistolary novel, which is one that's written in the form of a letter from one person to another. What sets Age of Iron apart is that the letter we're reading doesn't seem to have a distinct beginning or end; it reads more like an extended journal. On one hand, it seems pretty great that Mrs. Curren has the chance to write this letter to her daughter – it gives her the opportunity to say all the things she might not be able to express over the phone. The contents of her letter range from the most important stories in her life to more mundane details, including many reflections on even just the process of writing.
Yet, we have to wonder if her daughter is actually ever going to get her hands on these letters. Mrs. Curren has to depend on Vercueil to send them off (why she can't do it herself in increments is a question that goes unanswered through the book). While Vercueil promises to send them on Mrs. Curren's behalf, we never find out if he actually does. Still, Mrs. Curren sees Vercueil as her "messenger." In a way, the written form of the novel is a key way in which Coetzee creates a relationship between Mrs. Curren and Vercueil because it shows just one out of many ways in which Mrs. Curren comes to depend on him; the original intent of the letters almost seems to fade into the background.