In Harper Lee's To Kill a Mockingbird, the children are too quick to believe the rumors that have been spread by the gossips, the uninformed, and the superstitious.
Because Boo Radley never comes out, they see him much the way his family has made the community see him: as a ghost, a non-person. His humanity has been taken away from him, and the children envision him in a very one-dimensional way. After the fire, when Boo put the blanket around Scout's shoulders, they seem to somewhat lose their sense that he is a complete monster with jagged teeth who eats squirrels, though because they fear the house and the rumors, they still fear Boo to some extent.
Because of the child-like gifts left in the tree, the childish stitching on Jem's pants and his unobtrusive presence, the children perhaps begin to see him as if he is one of them. (Even though they are completely sure at the beginning about who has left the gifts or sewed the pants.) They don't understand that he has been abused and his very spirit crushed: I doubt anyone in town realizes this.
Perhaps the way that they misjudge Boo the most is in believing he is powerless. Once again, I think the adults could be accused of the same mindset. To the town, Boo is like an old, faded photograph. He is a part of the past that no one thinks much about—expect Atticus as he tries to keep the children away to preserve Boo's privacy.
The irony in their misjudgment of Boo is revealed under the most dire circumstances: Boo leaves his home, perhaps to follow them and watch them—maybe drawn by Scout's costume—and he ends up saving their lives. By the end, however, Scout is able not just to see that Boo is so much more than a shadow, but that there remains within him the remnants of the southern gentleman his parents started to raise before he got into trouble. When Scout walks Boo home, with her hand tucked in the crook of Boo's arm, Scout is sure that even Miss Stephanie could not have found fault with Scout or Boo's behavior, as if Scout were any young lady out for a civilized walk with a young man.
Of course, in reality, though Boo is an unlikely hero, when he returns home, he becomes a ghost to Maycomb again. Boo will live on in the memories of the Finches and Heck Tate as much more, but Scout notes that once she leaves him at his house, she never sees him again.
They belive all of the rumour about him, and think that he is a monster. They never step in his shoes or as atticus says "you must get in someones skin and walk around in it to ready know what it feels like to be him"(that is not the actual quote but it is like that). Once Atticus explains his action and what it is like to be him they understand him more. How he likes to be alone and not see/known. At the end of the book you learn alot about. (you should re-read it)