Several years ago I did extensive college-level work on the writings of Flannery O'Connor. I found two books particularly helpful in understanding the fullness of O'Connor's achievement, this book and Brian Ragen's "A Wreck on the Road to Damascus." Baumgaertner writes from a similar theological perspective, and though I do not believe she is a Roman Catholic as O'Connor was, she writes with understanding and sympathy for O'Connor's position. I bring up the religious issue only because any in-depth study of O'Connor must face the fact of her deep commitment to her beliefs.
The books is very readable, and though Jill Baumgaertner is a professor (at Wheaton College, Illinois) she takes pains to avoid the academic jargon that marrs much critical writing today. If what you want is a sympathetic insightful reading of O'Connor then there is no better book to start with. However, if what you want is "hip" academic jargon then read Kreyling's collection.