There have been two exceptions to this woeful lack of perception on my part. The first time I watched "The Sixth Sense," I guessed that Bruce Willis was a ghost about three scenes in. I have no idea where I got that from. I thought it was so obvious that I was surprised to learn that everyone else was surprised at the end.
The second exception is with "Shutter Island." The very first time I saw the trailer for the movie, I was only half paying attention. Even so, I thought "Oh, I bet the secret is _______." I was so convinced I was correct that I decided to read the book instead. Because it struck me as kind of a cheesy Big Secret, and I thought that the book would give a lot more supporting evidence and be a better time.
I was right on all counts. I'm not bragging. I mean, trust me - this NEVER happens.
I'm not going to tell you what the Big Secret is. Odds are you have heard already, because the general public is not very good about avoiding spoilers. People who saw the movie are generally annoyed, and I can understand that. A movie is naturally going to have to gloss over and toss out a ton of stuff from the book. And it's those little things, the odd little discrepancies, the repeated incongruous themes, which really make the story.
Suffice it to say that there is a Big Secret. This is essentially a detective book on two levels. At the superficial level, it is a detective book which sends a federal marshal into a desolate and creepy asylum for the criminally insane, in order to track down a prisoner who escaped from a locked room under close supervision. At the deeper level, the reader is the detective. The book leaves many clues, if you pay close enough attention.
"The Sixth Sense" worked so well because it's still a good movie, even if you know the Big Secret. You can watch the movie again and admire the craft and storytelling. And the story itself is still compelling. I would say that Shutter Island is only good if you DO know the Big Secret. There are a lot of aspects of the story that would seem downright idiotic, if the book was playing it straight. But watching how all the pieces fit together is an intriguing and satisfying process if you already know the end result.
Ultimately, Shutter Island is a great little lightweight summer read, a nice little mental puzzle. But the double whammy of an unreliable narrator and "none of this is real" has the unfortunate side effect of preventing the reader from making an emotional connection with the story. Without that emotional connection, Shutter Island is little more than an intellectual exercise.