One aspect of Canticle I always admired was how the tempo of the book mirrors technical innovation. The book, which depicts a postapocalyptic society stuck in a kind of medieval dark age, starts out at a very slow pace (something I've seen readers complain about), and relatively little happens at first, but as this society starts discovering technology from the past, the pace picks up, and by the end of the book we've gone through hundreds of years of technological progress.<p>The book isn't perfect. The huge jump in time between each part of the book means that the plot essentially starts over in acts two and three, and you lose the continuity of character development. This was the result of Miller constructing the book from three separate short stories (heavily modified and greatly expanded), and is necessary in order to tell the story as it's designed, but it makes for a somewhat frustrating reading experience. Still, it's obviously a classic for many other reasons.
It's too bad Miller never wrote much after he published it. (I've not read the sequel.) Apparently he spent the rest of his life battling depression and writer's block, and committed suicide before he was able to publish anything else.