It is sometimes unfair to describe an author's writing in a single phrase. However, Andre Norton's stories, more easily classified than many, might be called "romantic adventure"—akin to tales of island castaways, cowboys and indians, and knightly quests. Her heroes are of epic size; her books, filled with action, peril, and mystery, are rich with complex and colourful descriptions of settings, characters, and societies.
Certain themes occur in story after story, There is the "beast master" theme, a quasi-symbiotic relationship between men and animals that involves some kind of direct mind-to-mind communication. There is the "space-opera," often involving a galactic empire (or two). There is the "ancient race" theme, the concept of an old and mysteriously powerful culture that lurks in the background. There is time travel, and the aftermath-of-atomic-war theme. In addition, nearly all books written since 1963 contain the themes of witch powers and parallel universes.
P. Schuyler Miller claims that a prime attraction of this author's writing is that she introduces many intriguing ideas that are never completely wrapped up at the end of the book, thus leaving something to be filled in by the reader's own imagination. He points out that her stories are ageless in the sense that they are set on exotic and far-flung worlds that science cannot make commonplace (at least in the foreseeable future). But despite everything in her favour her work is stigmatised by the appellation "escape literature." (p. 129)
[Why is there an] absence of critical recognition and what can we expect from here on?
During the Fifties and early Sixties literary interest in s.f. shifted to "mental" or subjective events, viewed in themselves or in their relationship to external events in the "real" world—with the adventure story being relegated by critics to the domain of juvenilia. This "demotion" made it easy for critics to dismiss Andre Norton as just another female writer of children's books. (Without trying to settle the question of what is important or acceptable as science fiction, I can observe the snobbery of ignoring work simply because it does not bear the stamp of currently "important" writing.)
Recent years, however, have seen a revival of interest in the fantasy adventures of [Edgar Rice] Burroughs, [Robert] Howard, [Ray] Cummings, and [A.] Merrit …, each of whom offers escape to a world more "natural" than our own, where existence is unspoiled by the artificialities of urban civilisation. Of course, Andre Norton returns directly to the primitive mode only in her beast-master and aftermath-of-atomic-war themes, but in each instance the hero's courage and resourcefulness accomplish what city-bred degeneracy could not. Although her writing lacks a single archetypal figure to represent our primitive selves (like Tarzan or Conan), it belongs to the same general class as Burroughs' and Howard's and so, I believe, will be given the same critical attention these authors are starting to receive.
Also, with her recent Witch World series, Norton shares the literary primitivism exemplified in the Sword and Sorcery of veteran contemporaries like [Fritz] Leiber and [L. Sprague] de Camp and newer writers like Ted White, Michael Moorcock, and Lin Carter. Amongst this group, perhaps, Andre Norton will receive the type of recognition she lacked while apart from any other. (pp. 129-30)
Barry McGhan, "Andre Norton: Why Has She Been Neglected?" in Riverside Quarterly (copyright 1970 by Leland Sapiro), January, 1970, pp. 128-31.