"Good Country People" is one of O'Connor's most famous stories and different readers will find different meanings in this work.
The story certainly seems to have a lot to say about appearances. The work's central character is named Joy, but she certainly does not seem to be a very joyful person. In fact, she has changed her name to Hulga, which sounds a lot like the words "hulk" or "ugly."
Manley Pointer is a Bible salesman, but he knows very little about the Bible and in reality behaves more like an incarnation of the Devil than one would expect a Bible salesman to behave. Indeed, he cannot even pronounce the word "Christian" correctly.
Whereas Manley Pointer does not appear to be very intelligent, Joy-Hulga (like O'Connor herself) is a highly educated woman. Joy-Hulga assumes that her intelligence will easily defeat that of Manley Pointer, whom she regards as a simpleton.
Ultimately, though, Joy-Hulga learns that she should not judge a book salesman by his "cover." Manley Pointer tricks Joy-Hulga and steals her wooden leg.
Even as Pointer flees the farm with the wooden leg, Joy's mother does not realize what a wicked fellow he is:
“Why, that looks like that nice dull young man that tried to sell me a Bible yesterday,” Mrs. Hopewell said, squinting. “He must have been selling them to the Negroes back in there. He was so simple,” she said, “but I guess the world would be better off if we were all that simple.”
Thus, while O'Connor's story will have a variety of interpretations, one of the central themes of the work appears to be about the need to look at people in a way that goes beyond just the superficial.