Margaret Mitchell's bestselling novel Gone With the Wind (1936) makes several appearances in The Outsiders. Like the sunrise, it's one of the things that connects Pony and Johnny. By buying the book for Pony in the first place, Johnny shows how considerate he is, and how observant. Pony doesn't even remember mentioning that he wanted to read it.
So, what does a novel about the U.S. Civil War have to do with The Outsiders? Well, we can start with a broad definition of "civil war." Basically, a civil war is a huge fight between members of the same country or group. Isn't this what's going on with the Greasers and the Socs? They're all residents of the same city. They even go to the same school. Yet, they're locked in a battle in which one group – the Socials – seeks to dominate and control the other group – the Greasers. Although this is certainly not on the scale of the U.S. Civil War, this gang battle is loosely based on the same principles, and includes casualties, weapons, battles, and other hallmarks of war.
We find it interesting that Pony doesn't finish reading the novel. The book will, for him, be a symbol of Johnny and Johnny's "unfinished" life, a life he gave up in order to do something he considered meaningful and important – saving the little kids from the fire. Johnny is, for Pony, gone with the wind. Still, he's left something behind for Pony, tucked into his copy of the book. The letter (discussed in Johnny's "Character Analysis") inspires Pony to take up a different kind of weapon to fight his battle –his pen, which Pony uses to nonviolently transform his world and to positively shape the worlds of other boys like him.