The tone of any specific place is affected by the surroundings and also by the people present. Just as in real life, the tone in books is influenced by the settings and the characters that are there. In To Kill a Mockingbird by Harper Lee, the tone of the story is affected by the metaphors and imagery surrounding the settings and the characters.
Using imagery, Harper Lee manipulates the setting to mirror the many moods of each page. For instance when she is describing Maycomb. "In rainy weather the streets turn to red slop; grass grew on the sidewalks, the courthouse sagged on the square. (Pg. 5)" The grass growing on the sidewalks shows that Maycomb is kind of an wild/untamed town. The courthouse sags, a sagging building tends to lean to one side; in this case, the courthouse leans towards or in favor of the white population. Putting this together, you can determine that this a very old fashioned town, giving you a very mild calming tone. The second example is in which Scout describes the Radley Place: "The Radley Place jutted into a sharp curve beyond our house. Walking south one faced the porch; the sidewalk turned and ran beside the lot. (Pg. 8)" Boo's house juts into a corner, forcing its existence into Maycomb because it doesn't belong. The house faces the South, which is away from the sunlight, afraid of seeing it such as a phantom or a vampire would be. The sidewalk ran besides and past the house, just like Jem does when he passes it. It is as if the presence of the house scares even the sidewalk. This gives the house a haunted spooky tone.
The tone of the story can also be affected by the words describing a certain character. For example, the describing of Calpurnia. "She was all angles and bone; she was near sighted; she squinted; her hand was as wide as a bed slat and twice as hard. (Pg. 6)" Being all angles and bones you would have to be careful how you treat her, otherwise you would be poked.