It may be Randian in its inspiration, but it still will always be a prog rock masterpiece. My favorite movement in it is soliloquy, not only for that killer Alex Lifeson solo, but also Geddy Lee's earth-shattering wails.
Rime of the ancient mariner is a good example, but I didn't want to stick a style/genre on it because I'm sure there's stuff outside the genre that does something similar. Long songs telling some sort of story.