The novel opens in the 26th century with a young monk in the desert southwest of what used to be the United States. He accidentally falls into a small cavern which turns out to be a fallout shelter with artifacts from the late 20th century. Amazingly, the artifacts include personal items from I.E. Leibowitz, the founder of the monk's order. The order's charter is to preserve scraps of knowledge from the pre-apocalypse society that was destroyed by what they know as the Flame Deluge.
Over the next 12 centuries civilization is reinvented while the monks continue their role as guardians of the past. The real question is whether things will turn out differently this time.
Canticle is both a perfect reflection of the Cold War era in which it was written and a timeless classic that considers the true nature of man. My favorite quote from the book is this rather long one.
The closer men came to perfecting for themselves a paradise, the more impatient they seemed to become with it, and with themselves as well. They made a garden of pleasure, and became progressively more miserable with it as it grew in richness and power and beauty; for then, perhaps it was easier for them to see that something was missing in the garden, some tree or shrub that would not grow. When the world was in darkness and wretchedness, it could believe in perfection and yearn for it. But when the world became bright with reason and riches, it began to sense the narrowness of the needle's eye, and that rankled for a world no longer willing to believe or yearn.It's mere coincidence that I recently finished reading Ken Follett's The Pillars of the Earth, another sweeping novel centered around monks and their abbey. Let's not infer too much from how central religion is to both plots. It's interesting to look back to Pillars' 12th century monks who were historically the center of knowlege and then extrapolate that same role to Canticle's monks - if they did it before, there's no reason why they couldn't do it again.
Whether or not you're a nuclear or post-apocalyptic fan, I highly recommend A Canticle for Leibowitz. Many reviewers have said this is a book they've re-read numerous times and I can see myself doing that too.