A crumbling Irish estate and its successive generations of owners become the subject of a narrative pieced together by a devoted servant. The story unfolds through the recollections of the loyal housekeeper, Thady Quirk, who chronicles the decline of the Rackrent family and their ancestral home. The novel explores themes of inheritance, social change, and the often-unreliable nature of memory, as Thady attempts to present a favorable, albeit biased, account of his employers' fortunes and follies.

Castle Rackrent is widely recognized as a significant work of early Irish fiction, often lauded for its innovative narrative voice and its sharp social commentary. Critics frequently highlight Maria Edgeworth's skillful use of Thady Quirk's unreliable narration to expose the follies and eventual ruin of the Rackrent family. The novel is praised for its blend of historical insight and satirical wit, offering a complex portrait of the Anglo-Irish landed gentry during a period of significant social and political upheaval. Its influence on subsequent novelists, particularly in the development of the novel of manners and historical fiction, is also a recurring point of discussion.