I whole heartedly support surprise endings. In fact, if an author can catch me off guard at the end of a book, I am very pleased. What I do not like is "surprise" endings that don't make sense. I recently read a book and when it was over, I was angry. I tried to evaluate why I was angry. I thought, am I angry because my prediction of how it was going to end was wrong? I really didn't think I was that shallow (at least not this time anyway). I came to this conclusion:
Surprise endings where you can say, "OH. That makes total sense" and then you can look back through the book and see everything you missed the first time and feel like you're discovering a whole new plot = good surprise ending.
Surprise endings where you think to yourself, 'Uh, did the author just throw that in so that nobody would be able to guess how her book ended because it makes absolutely no sense and, in fact, is the exact opposite of what the book was building up to and purporting itself to be.' = bad surprise ending.
I won't say the name of the book because I don't want to ruin it for anyone else. But I'm still mad. (oh, in case you read my last last post, it's not Cindy's book.)