The first and most important step to answering a question on a whole book is to make sure you have read it. Once you have, you can identify whether a technique (like digression) or a theme (like jealousy) is present, and, if it is, how important it is in changing how we read the book. In response to this question, we would first identify what ‘digression’ is. Only when we know what it is can we identify where it happens and why it is important. Ideally, you would re-read the book so that you can carefully identify the appearances of this technique. You can do this by skim-reading! If you are pushed for time, skim-reading is fine. While you read, record the examples of digression on paper. When they are in the same place, you can see what the common theme is - what do they make you think about the narrator and how he tells the story? Your thesis might be different from your classmates - your friend might think it means that the style of narration is more realistic (like a normal conversation), but you might think it makes the narrator seem mentally deranged. Either is fine, but you must be prepared to explain why! For example, if the tone is realistic, it might bring the reader closer to the story and become more invested in the characters and the plot. On the other hand, if the narrator seems mad because he can’t stick to one path, it might make the reader not trust what they are told. When you have decided the main argument, you can structure the essay by the effects that the digression has on the audience and how the techniques within the book contribute to the overall thesis. As this is a big essay question, I would help you identify the key parts of the essay structure and fill them in so that writing your answer becomes less daunting.