I've included a link below with a thorough explanation of themes, but let me cover just a few for you now. Obviously, the American family and the ideas of religion and/or spirituality are center to the story. This two-part book focuses on two siblings in a large family, and through their experiences, the audience is exposed to the dynamics of the whole family. Family influences who a person is. Franny and Zooey both are shaped by the death of Seymour and the abandonment of Buddy. In a way, these events that occurred in their family, of which they have had no control, have stunted the growth process of these two characters. They did not have the full sibling and family experience, and so they were not able to fully grow up. Their names give away their immaturity, being childish nicknames.
The book that was left behind by Seymour is "The Pilgrim Continues on His Way." Franny's interest in the book underlines another theme, that of religion. What is it to be religious? Does being religious mean that we have to follow the rules of the Church? Or can a person be spiritual and fulfilled without being subservient to organized faith? These questions are pursued by Franny, with help from Zooey. Examine Father Waker - as a symbol of religion, readers would expect him to be comforting to his family. Instead, he has disappeared to South Africa and failed to communicate with them.