Boo Radley is a fascinating character. When we are first introduced to him we learn that he will be important, but he is still a mysterious and spooky figure.
The Radley Place was inhabited by an unknown entity the mere description of whom was enough to make us behave for days on end. (ch 1)
Boo also has a rocky history.
According to neighborhood legend, when the younger Radley boy was in his teens he became acquainted with some of the Cunninghams from Old Sarum, an enormous and confusing tribe domiciled in the northern part of the county, and they formed the nearest thing to a gang ever seen in Maycomb. (ch 1)
From these descriptions, you would expect Boo to be a terrible person or a monster.
Boo wasn't crazy, he was high-strung at times. It was all right to shut him up, Mr. Radley conceded, but insisted that Boo not be charged with anything: he was not a criminal. (ch 1)
The story begins to seem more sad than scary. Boo is locked in the Radley house.
Jem gave a reasonable description of Boo: Boo was about six-and-a-half feet tall, judging from his tracks; he dined on raw squirrels and any cats he could catch, that's why his hands were bloodstained-if you ate an animal .raw, you could never wash the blood off. There was a long jagged sear that ran across his face; what teeth he had were yellow and rotten; his eyes popped, and he drooled most of the time. (ch 1)
Of course, this is a fanciful description of Boo and not an accurate one. The children continue to play their game demonstrating Boo’s life story, or their version, for the neighborhood.