The story is recounted from the first-person perspective of Edgar Drake. Edgar is the main character of the story, so it makes sense that readers see events through his eyes. Edgar is a very reasonable, kind and quiet man, and so he is easily sympathetic to the reader. This means that many of his reactions are similar to what the reader's own reactions might be, such as fascination concerning different cultures, shock at the little boy's death, sympathy for Carroll's intentions, and sadness at the way the Burmese are treated by the British. Because the reader can share Edgar's views, this makes it easier for the author to draw messages about imperialism and war from the events of the book.
The Piano Tuner