Why so much dialogue?

The first part of Foe is very different from the other books we have read. The majority of the lines in this book are in quotes, which was not the case in Cat’s Cradle or The Things They Carried. Though otherwise the books might read similarly, the fact that Foe is only quotes so far changes how I read and understand the novel. Instead of being told a story from a narrator’s point of view, we are hearing the stories through character’s dialogue.  The previous two books read as if the narrators were speaking directly to the readers. For example, in the chapter Good Form of The Things They Carried, the narrator Tim says “I want you to feel what I felt.” Also the Jonah says, “Listen: When I was a younger man...” in Cat’s Cradle. As the reader, I felt as if those lines were directed and intended for me. However in Foe, the lines I have read so far are not spoken to the reader. We are reading half of a dialogue. It is very different reading stories told by Sarah Barton to another character than stories told by a narrator to the reader. I think this changes how we read and analyze the stories and meaning behind them. This demonstrates that in order to understand a story, it is not only important to analyze the storyteller, but also to recognize the intended audience. But why did J.M. Coetzee choose to do this? What’s the purpose and how does it affect the reader’s experience of Foe?