Set in a Catholic monastery in the desert of the southwestern United States after a devastating nuclear war, the book spans thousands of years as civilization rebuilds itself.

The monks of the Albertian Order of Leibowitz preserve the surviving remnants of man's scientific knowledge until the world is again ready for it.

The novel is a fix-up of three short stories Miller published in The Magazine of Fantasy & Science Fiction that were inspired by the author's participation in the bombing of the monastery at the Battle of Monte Cassino during World War II.

It won the 1961 Hugo Award for best science fiction novel, and its themes of religion, recurrence, and church versus state have generated a significant body of scholarly research.

[1] Significant themes of his stories included loss of scientific knowledge or "socio-technological regression and its presumed antithesis, continued technological advance", its preservation through oral transmission, the guardianship of archives by priests, and "that side of [human] behavior which can only be termed religious".

This experience impressed him enough to write, a decade later, the short story "A Canticle for Leibowitz", about an order of monks whose abbey springs from the destroyed world around it.

[5][6] The story, which would evolve into "Fiat Homo", the first of three parts of the fix-up novel, was published in the April 1955 edition of The Magazine of Fantasy and Science Fiction (F&SF).

It was while writing the third story, "The Last Canticle", for magazine publication in February of the following year[7] that Miller realized he was really completing a novel: "Only after I had written the first two and was working on the third did it dawn on me that this isn't three novelettes, it's a novel.

This full-length novel has a tripartite structure: each section is "short novel size, with counterpoint, motifs, and allusions making up for the lack of more ordinary means of continuity".

Eventually concluding that his wife was dead, he joined the monastery, took holy orders (becoming a priest), and dedicated his life to preserving knowledge by hiding books, smuggling them to safety (known as "booklegging"), memorizing, and copying them.

The Order's abbey is located in a remote desert in New Mexico, possibly near the military base where Leibowitz worked before the war, on an old road that may have been "a portion of the shortest route from the Great Salt Lake to Old El Paso".

Six hundred years after his death, the abbey still preserves the "Memorabilia", the collected writings and artifacts of 20th-century civilization that survived the Flame Deluge and the Simplification, in the hope that they will help future generations reclaim forgotten science.

When Brother Francis picks up the rock, he discovers the entrance to an ancient fallout shelter[a] containing "relics", such as handwritten notes on crumbling memo pads bearing cryptic texts resembling a 20th-century shopping list.

Abbot Arkos, the head of the monastery, worries that the discovery of so many potentially holy relics in such a short period may cause delays in Leibowitz's canonization process.

The narrative then focuses on the buzzards who were denied their meal by the burial; they fly over the Great Plains and find much food near the Red River until a city-state, based in Texarkana, rises.

Meanwhile, Hannegan makes an alliance with the kingdom of Laredo and the neighboring, relatively civilized city-states against the threat of attack from nomadic warriors living on the plains.

The Wanderer reappears at the rectory, at the last meal before Brother Joshua and the space-trained monks and priests depart on a secret chartered flight for New Rome, hoping to leave Earth on the starship before the cease-fire ends.

After the abbot's death, the scene briefly flashes to Joshua and the Quo peregrinatur crew, who are preparing to launch as the nuclear explosions begin.

Joshua, the last crew member to board the starship, knocks the dirt from his sandals (a reference to Matthew 10:14, "If anyone will not welcome you or listen to your words, leave that home or town and shake the dust off your feet"), murmuring "Sic transit mundus" ("Thus passes the world", a play on the phrase sic transit gloria mundi, "thus passes the glory of the world").

Scholars and critics have noted the theme of cyclic history or recurrence in Miller's works, epitomized in A Canticle for Leibowitz.

[15] David N. Samuelson, whose 1969 doctoral dissertation is considered the "best overall discussion" of the book, calls the "cyclical theme of technological progress and regress ... the foundation-stone on which A Canticle for Leibowitz is built".

The action of the second part, "Fiat Lux", focuses on a renaissance of "secular learning", echoing the "divergences of Church and State and of science and faith".

"Fiat Voluntas Tua", the final part, is the analog of contemporary civilization, with its "technological marvels, its obsessions with material, worldly power, and its accelerating neglect of faith and the spirit".

[18] Literary critic Edward Ducharme claimed that "Miller's narrative continually returns to the conflicts between the scientist's search for truth and the state's power".

Also unimpressed, Time said, "Miller proves himself chillingly effective at communicating a kind of post-human lunar landscape of disaster", but dubbed it intellectually lightweight.

[23] Rating it five stars out of five, Floyd C. Gale of Galaxy Science Fiction said that "It has many passages of remarkable power and deserves the widest possible audience".

[24] A decade later, Time re-characterized its opinion of the book, calling it "an extraordinary novel even by literary standards, [which] has flourished by word of mouth for a dozen years".

[30] Fellow critic David Cowart places the novel in the realm of works by Evelyn Waugh, Graham Greene, and Walker Percy, in 1975 stating it "stands for many readers as the best novel ever written in the genre".

[32] Scholars and critics have explored the many themes encompassed in the novel, frequently focusing on its motifs of religion, recurrence, and church versus state.

In addition to recounting his travels as Cardinal Brownpony's personal secretary, the book describes the political situation in the 33rd century as the Church and the Texark Empire vie for power.