This appears to be the only critical work ever published about E.M. Delafield, and has been out of print for some time. My copy came (via Amazon) from the withdrawn stock of the South Dakota State Library; it doesn't look like anyone in South Dakota ever borrowed it.
McCullen's work begins with a short biography, then goes on to review EMD's books and some of her journalism. His analysis is strongly biographical in tone; this is reasonable, up to a point, given the autobiographical nature of much of EMD's work, and he does consider the difference between the narrative voice of the Provincial Lady, and her creator. He also offers a psychological interpretation of some of the major works, and considers EMD's approaches to form. EMD's output was large, and he argues persuasively that the standard of her achievement might have been generally higher if she had restricted this; however, he also appears convinced that her best books are very good indeed.
This is a fairly short work, which works well as an overview of EMD's work and a critical introduction to her methods and themes. McCullen notes the need for a feminist evaluation of her work, to support his claim that she deserves "a place, however small, in the Great Tradition".