Answer:
The tone of a novel refers to the attitude and manner of speaking of the story's narrator. So the first thing to do is to concentrate on what the narrator is saying and determine how he says it. This is easy to do in obviously narrated stories such as 'Heart of Darkness' or 'Don Quixote' and easy also for stories written in the first person. Some stories however has the narrator suppress to near invisibility and it is difficult to attribute a tone to the story at all.