Critical study plumbs Fuentes; Carlos Fuentes, by Wendy B. Faris. New York: Frederick Ungar Publishing Company. 241 pp. $14.50 in hard cover, $6.95 in paperback.

Wendy B. Faris's comprehensive, critical study of Carlos Fuentes, the Mexican novelist and critic, is the first of its kind in English. As such, her literary analysis deserves our attention as much for the importance of its subject as for what she accomplishes.

Fuentes has been a prominent figure in the recent dynamic growth of Latin American fiction. In 1982 his friend, the novelist Gabriel Garcia Marquez, won the Nobel Prize for Literature. Although the two authors have shared a common political ideology, their most important link has been a remarkable kind of narration seen in the works of each, which blends marvelous images with poetic prose.

Such writing is not only strange, it is magically strange; hence the term by which it has come to be known: ''magical realism.'' To read Fuentes is to see the world in a multicolored mirror. Smooth white stones become dinosaur eggs; a witch seduces a young man by transforming a rabbit into a lissome beauty; a door knocker becomes a grinning dog's head. In the world of magical realism, psychological reality is to be found in the unexpected exaggeration of ordinary events. Like the output of other great writers, Fuentes's works have been of uneven quality. A few of his novels may be considered flops.

With the publication of ''Where the Air is Clear'' in 1956, however, he established himself as a major writer. International critical acclaim and popularity followed the publication of ''The Death of Artemio Cruz'' in 1962. Those two works offer the clearest examples of Fuentes's obsessions with indigenous Mexican mythologies and national identity.

In both novels there is a strong sense of sadness and resignation. The Fuentes fictional map is filled with places that share mixed indigenous and colonial names and inhabitants who have the peculiar duality of the outcast, never having been anywhere but seemingly without a place or a past.

In ''Carlos Fuentes,'' Professor Faris ignores the questions of Fuentes's niche in modern literature and prudently focuses on the unique achievements of his work: brilliant images, subtle narrative structures, and a literary anthropology of the third world.

Professor Faris has an excellent command of the Spanish language; her translations of key quotations and phrases are impeccable. More important, her illuminating perspective opens up the kind of plural readings of a given passage that greatly reward our reading of Fuentes. This kind of exegesis is sometimes necessary, given the complex, multilayered vision Fuentes offers - not to mention a style that is often opaque in the ablest of translations.

Faris's commentary, however, need not have been so exhaustively textual. One consequence is that we learn little of Fuentes as a person, nothing that gives meaning to the artist's unique struggle with himself, his origins, and his demonic calling.

Nonetheless, we owe Professor Faris a measure of thanks for her discussion of what might be called the communal imperative of the Fuentes novel. Through her analysis we see the mystical, even optimistic design in stories where the protagonist is headed for an unhappy end. In Fuentes only the group triumphs or seems to survive.