One important context that I need to provide for my students is background on O'Connor's Christianity. The most useful source here is O'Connor's own essays and lectures, which often explain how to read her works as she would have them read. Certainly O'Connor's pronouncements have guided much of the criticism of her work. I also find it important to address the question of racism in the story. I find Alice Walker's comments helpful here, on O'Connor's respectful reluctance to enter the minds of black characters and pretend to know what they're thinking.
Most criticism continues to be either religious or formalist.