I just finished "The House of the Seven Gables" by Hawthorne. I was struck by how often he switched tenses. Mostly the narration was in past tense, but then he would switch to present or even future tense. Sometimes the tense would change for a sentence or a paragraph; other times it would change for a whole chapter. It was a bit jarring, since it's hardly ever done, to the point where it is almost an iron-clad rule. (As in: Any competent editor or English teacher will always mark it wrong.) But it worked well the way Hawthorne did it in this novel. This set me thinking (and here's the question):
What are some (other) great examples where authors of novels successfully break the "rules" for writing? (And of course, what was the broken rule?)
I don't mean rule-breaking once in a blue moon, for dramatic emphasis. I mean a lot -- multiple chapters, or the whole book. And I'm restricting this to novels, because short stories are much more experimental. And by "successfully," I mean that the novel sold well and is fairly well-known. Also, I'm not necessarily asking for a list of ground-breaking novels, which broke "rules" that once seemed important but no longer stand.
Another example would be "Slaughterhouse-Five" by Vonnegut. (For a variety of reasons!)