A Canticle for Leibowitz is different from virtually every other post-apocalyptic book I've ever read. It's set centuries after the nuclear war that destroyed 20th century civilization, but what sets it apart is how it shows people trying to rebuild. It's both optimistic (humanity can rebuild, even from the worst) and skeptical about human nature. (Even knowing what the worst is won't stop people from courting disaster again.) The characters, especially the three stars, are memorable, though none of them are around for very long. The timescale here is massive, giving a sometimes painfully bleak look at the cyclical nature of history. It isn't entirely rough. There's humor, sometimes so black that I felt a little guilty to be laughing at it. It's also quite religious in nature, specifically Catholic. It's interesting, but not really surprising, that a highly organized religion like Roman Catholicism could survive nuclear war. Absorbing, frightening, and sadly realistic, A Canticle for Leibowitz is one of the best post-apocalyptic novels I've read.