'Canticle for Leibowitz' is often known as one of the most literary of the famous sci-fi novels. It was originally written in three parts, each one published in as a novella in a magazine. When it was put together for a single book, Miller kept the three stories distinct, though they are based on a common location and history.
The first part takes place some centuries after a full out nuclear war, then known as the Flame Deluge. One of the remaining splinters of civilization is a monastery in the southwest that is dedicated to preserving any scrap of writing that exists from the pre-war civilization. This part of the story centers on a young novitiate who chances upon a wanderer in the desert. This chance meeting leads to discovery of old materials and sets the young man on an unwanted path to noteriety. This one was my favorite.
The second part takes place some centuries later still, as the civilized world is rediscovering some modern sciences and inventions. The focus here is the sometime tension between science and religion and the way that politics can complicate both of them. Probably the weakest of the three.
The last story is centuries later again. This time the world is on the brink of nuclear war again. The church is working on sending missionaries offworld so that some part of the church will survive if the worst happens. The main focus is on a situation where the church is asked to bless euthanasia. It's heartrending.
I first read this book some twenty years ago. Back then, my Dad was teaching it in his Humanities class. 'Canticle' has interesting things to say about the role of organized religion in the world and interesting questions too. It's very well written and I'd recommend it to anyone that enjoys a good read. A great book.