I think that it's fair to say that in any given book, if half the readers go, "Oh!" at The Big Reveal and half go "Wait, WHAT?" but then the "Wait, WHAT?" people go back and read the last page again and at least 35% of them join the "Oh!" people at that point, then in my opinion that's the way I like to read/write. I don't mind if I'm in the "Wait, WHAT?" group on the first go-round (in fact, that tells me that the book passes the "subtlety" test, so I like that) but I do want to get it by the time I go back and read the last page again. If that made any sense at ALL.

I don't have to like the character(s) as long as I can match the headspace of someone, preferably the protagonist. And if it's a first-person POV it needs to be the narrator. (That's a post of meta all by itself!)