Flannery O'Connor's "Occasional Prose," here selected and edited by Sally and Robert Fitzgerald, includes a number of essays and lectures which are not only crucial in understanding her particular creative venue and vision but obligatory in understanding the the quintessential aspects of the novel or the short story. Of these, "The Nature and Aim of Fiction" and "Writing Short Stories" expand on the meaning of the book's title: Flannery O'Connor felt that the "mystery of our position on earth" is the heart of any fictional experience and that manners, or what she called the texture of existence, should reveal it. Other pieces deal with more specific aspects of writing or of being a Southern writer (Miss O'Connor maintained a definite literary Mason-Dixon line, opposing the Southern grotesques with their Northern equivalents--the man in the grey flannel suit) or of being a Catholic writer, and certainly all of her work attested to the artistic seriousness of purpose and spiritual convictions which are articulated here. With occasional lighter moments--the charming introductory piece on her peafowl, and even more occasional humor (". . . a Georgia author is a rather specious dignity, on the same order, as, for the pig, being a Talmadge ham"). This posthumous collection should not be confined to the author's enduring admirers--these are affirmations and illuminations of the innate creative experience--a special state of grace which a few writers, like Miss O'Connor, achieved.