I just finished Canticle for Leibowitz and i have to say this is some of the finer literature i've read in a long, long time. And I just got off Last Temptation of Christ before that, too. It's post apocalyptic fiction but basically don't think of any of the tropes of the genre, it's a really smart and inquisitive novel that tells the story from a Mad Max level, to a new renaissance, to an advanced civilization. It focuses on the Leibowitz chapter of Monks in the Southwest, who preserve any and all science and knowledge of the old world, painstakingly copying each copy they find for preservation. It's a great POV because most of the politicking takes place out of the scene, and what does happen is quite grounded. I'll be revisiting this novel again, no doubt about it.
I'm now in Princess of Mars, it's pretty shallow pulp at best, and feels just absolutely dumb compared to Canticle, but it's pretty damn fun adventure i simply cannot deny that. If it was good enough to be a striking influence on Sagan, it's good enough for me.