Tone is so important to a piece of writing that if the reader does not recognize it correctly, the meaning of the work is either mitigated or lost. For instance, imagine--as has happened in some high school classrooms--that a reader were to take Jonathan Swift's "A Modest Proposal" literally and not recognize the biting satire that is prevalent throughout his work?
Or, imagine that a reader miss the ironic tone in so many works? One example is Saki's short story "The Open Window" in which a young girl toys with a nervous visitor and, at the end, when she covers her act by telling her aunt another story, the narrator remarks that "Romance at short notice was her specialty."
There is no question that understanding the tone of a literary work is essential, for this tone conveys the authors' attitudes, and, thus, their purpose for writing the work. (a)