I'm putting the final touches on a short story commission, and feeling pretty good about the result. I like the ideas the piece explores, and feel like it has at least one or two things to say that haven't been said before.
The ending, however, was unbelievably difficult to get right. The final paragraphs center on an unexpected development; not a twist ending, per se, but definitely a shot out of the blue. Getting the timing right on the reveal has caused me no end of aggravation.
You see, the trouble with surprise endings is that there are basically two kinds of readers: Those who try to figure everything out in advance and those who wait to see what happens. If you write to the first group, the second one will flounder at the end, having not picked up enough clues to get the point. If you write to the second group, the first one will see the twist coming from lightyears away.
I have concluded that the only possible solution is misdirection. You must convince Group #1 that they have already figured out the surprise. They will then stop looking, and you can treat them as part of Group #2.