I enjoyed the very conversational, rambling style of Dolores Claiborne by Stephen King. Yes it’s just first person, but it’s a unique take on first person.

Another interesting style was Soldier of the Mist by Gene Wolfe. The narrator is a Greek or Roman soldier who had a severe traumatic brain injury and has anterograde amnesia, so every evening he writes down what has happened to him on a scroll and reads it back the next morning. Only sometimes the strolls get lost, or he isn’t able to write for a few days, and so there’s a lot of confusion and disjointedness. Throw in visions of gods and other supernatural elements, and it comes out to be quite an interesting read. At least, that’s what I remember from having read it many, many years ago.