Up until [the publication of A Canticle for Leibowitz] Miller had been regarded, in Sam Moskowitz's words, as "the perennially promising author." An engineer-turned-writer, he had published some forty-odd stories in the major science fiction magazines in the Fifties; several were chosen for anthologies, sometimes of the best stories in the field, but many of his tales are rather conventional and far from distinguished. "The Darfsteller," a story about a human actor struggling quixotically to compete in an age of automated stage plays, won for him a "Hugo" in 1955 for the previous year's best novelette, but he was not able to publish a collection of stories until after the success of his novel. The first collection, Conditionally Human (1962), combines "The Darfsteller" with two other novelettes, demonstrates his proficiency with fiction of medium length dealing with serious intellectual and emotional themes, and shows a generally prosaic and sometimes plodding style. The second collection, The View from the Stars (1964), consisting of nine stories from the period 1951–1954, exhibits a considerable range of subject matter, various degrees of control over style, and a talent for compression, and makes it clear that the ability to construct effective scenes and dramatic contrasts was present early in Miller's abbreviated career. Ironically, by the time these books were published, their author was no longer writing science fiction…. Nevertheless "the perennially promising author" had fulfilled his promise; his last work was one of the best novels ever to emerge from the pulp science fiction field.

A novel of about 100,000 words, A Canticle for Leibowitz is composed of three parts, roughly equal in length, sharing the same basic setting in space but separated in time by gaps of approximately 600 years. Each part is a coherent novelette, an original variation on a conventional science fiction theme, carefully plotted and constructed for its own particular effects. Each individual story, dealing with individuals' personal struggles, brings to life the issues and ideas of the whole which, because of the interplay between the novelettes, is thus something greater than its parts. Making good use of science fictional conventions, methods, and philosophy, Miller has gone beyond them to produce a dissertation on the ambiguity of advance and the relativity of knowledge, against a background of history as an aesthetic pattern, a seamless fabric into which individuals and institutions, actual events and folklore are inextricably interwoven. Yet for all the complexity, solemnity, and high seriousness that such a description (aptly) suggests, the book is first of all an entertainment, full of fun and occasional thrills, presenting sympathetic characters in a narrative of curious and interesting situations and events. (pp. 226-29)

As an entertainment, the novel is a story, or three stories, about people, about their joys and pleasures, about their thoughts, and about their personal struggles, with their faith, with their environment, with themselves. At this level, the reader is made to feel such things as survival, discovery, and frustration, which bulk so large in the intellectual content of the book, even as the comic effects amuse him and predispose him to sympathy with the characters. The comedy, however, and the irony congruent with the narrator's vast perspective make it nearly impossible to identify with the characters, leading us more toward a position of relating ourselves intellectually, to their philosophical stances, and to the oblique historical parallels with our own past and present. The characters, themselves, seem to find complete commitment to an idea difficult to achieve, however strongly they may be shown as wanting to believe in it, and their relatively cerebral involvement is reinforced by the narrator's rationality and perspective.

The typically science-fictional tendency to involve the head before the heart is evident in Miller's style, too, which is entertaining in the way that cultured, intelligent conversation is. Seldom startling, his style is witty, yet relatively formal, and distinctive enough to maintain an aesthetic distance between reader and story, encouraging critical observation and appreciation. Although the directness, obviousness, and simplification of pulp style had not been blatant in the original versions of the [three sections of A Canticle for Leibowitz as] novelettes, Miller added dignity to his revised narrative by means of longer sentences, more sonorous rhythms, and less use of colloquial diction. Specialized words from technology and theology were already in frequent use in the earlier versions, as were words and sentences from foreign languages, from Latin of course, but also from Hebrew (in Hebrew script, the English translation of which is given), with an additional snatch of German to bring us into the industrial totalitarianism of Part Three. The net effect is a certain measure of weight and seriousness and scope, contributing to the narrator's air of omniscience but also to the dignity of the characters, whose speeches often seem somewhat elevated and self-conscious. From the perspective of the centuries, dignity may seem a bit incongruous for such puny and even comic figures, but within each story, some characters manage to stand out, as if to decree their own significance on a purely human scale of values.

The mixture of comedy and weightiness which penetrates so much of the book is visible also on the symbolic level. The allegorical identification of Miller's three eras with eras in Western civilization suggests a certain solidity which we associate with historic grandeur. The allegory also impresses upon us the idea that these are representative men and times about which we are reading. But the disparity between Miller's relatively simple men and the inflated figures of history, and between his relatively uneventful narratives and the supposedly grand movements of history is essentially comic, a sympathetic but knowing commentary on the difference between aspirations and achievements. (pp. 271-73)

Through everything, of course, as in the Poet's book, runs a kind of laughter, although it is not the same bitter, sardonic laughter as that which the Poet displays in Part Two, and which presumably causes Abbot Zerchi to dismiss the book of verse as little more than satire. Irony is a major tool of both writers, but the Poet's irony is more limited, more personal, more intent on destructive criticism, and related to a sense of outrage that the world should be as it is. The irony of Miller's narrator is to a great extent the irony of vast perspective, against which personal outrage would be rather out of place. Miller's humor involves more than irony, however; his style is witty, his characters are sympathetically treated for all their bumbling, and his approach is intellectual rather than sentimental. His people have little to be thankful for or to look forward to, but they find joy in simple tasks and meaning in greater ones, and they delight as much in contemplation as they do in playfulness. The author too appears to delight in little things, in puns and comic allusions, in episodes of slapstick, in dramatic effects of confrontation, discovery, and anticlimax.

Humor of any kind is relatively rare in science fiction, with the exception of what James Blish terms "the painful traveling-salesman banter which passes back and forth over real drawing-boards and spec sheets." Perhaps because the scientist-author or the scientist-hero sees the world rigidly in terms of weights and measures and lines of force, perhaps because he is so busy seeking immediate solutions to mundane problems that he can't see himself from the perspective of anyone else, an even rarer occasion in science fiction is the evocation of the "comic spirit." All the more to be appreciated, then, is the achievement of Walter M. Miller, Jr., for, in A Canticle for Leibowitz, he has written a genuine comic novel. In doing so, however, he has not written a work of "pure" science fiction; rather, he has incorporated into his novel much of what is valuable in science fiction and discarded much that is worthless for his purposes. In other words, it would be more accurate to say about A Canticle for Leibowitz that it uses science fiction than to say that it is science fiction. (pp. 277-79)