I am curious as to what people think about why Boo begins to show himself more at the end of the novel. I know the reader is meant to think that Boo is this "malevolent phantom" at the beginning. Although, does anyone think he has experienced a maturation alike jem and Scout's.
Boo appears at the end to save Scout. He has been watching the children from afar, more as a guardian angel than a malevolent phantom. Throughout the book, as the children grow up they come to realize that Boo is more of a victim than a villain. As they get older, he begins to reveal himself to them in small ways. One example is with the gifts left in the tree. Another is when he puts a blanket on Scout's shoulders at the fire. Finally, when he sews and returns Jem's pants he reveals himself as a good force in their lives rather than a danger. At the end of the story, he solidifies his role by risking everything to stop Bob Ewell from killing Scout. He even allows her to walk him home (and asks her to). This demonstrates that the children have become as real to him as he has to them.
I think that Boo starts to show himself more because he has something to live for, as it were. Early in the novel, Boo would not have had anyone to identify with or care about in the outside world.
However, as the story goes along, Boo starts to identify with the Finch kids. He leaves stuff for them in the hole in the tree. He wraps Jem up with the blanket. These kids are his first real contacts with the world and these contacts make him care about them enough to finally show himself even more at the end of the novel.
So I think that he comes out because the Finch kids have given him someone to care about and feel connected to.