Kurtz is best known for the Deryni novels and short stories. Her 1970 debut novel, "Deryni Rising", was one of the first fantasy novels written in a mode closer to historical fiction than to mythology or legend, as was common in the then-popular high fantasy works such as those by J. R. R. Tolkien. Writing in "Strange Horizons", Kari Sperring calls Kurtz the "first writer of secondary-world historical fantasy", noting her close attention to the importance of faith in pre-modern Western societies and her portrayal of magic as a formal, ritual practice as opposed to the "picaresque and informal" way magic was depicted in other fantasy of the time.