*spoilers*
I haven't seen the film but I was given the book by someone that suggested I read it.
I'd read a few posts from this thread so I knew something was up but not what, I'd read about someone being unsure of their gun (I now know this was Chuck).
So I had guessed that something was rotten and thought that Teddy would be forced to stay on the island, that someone would either portray him as insane or drive him insane, but had no idea what would actually happen, it was a surprise to me and I thought the book was excellent. It being 5.37am and me having just finished reading is testament to this I suppose.
I'm definitely interested to see the film now, but I suppose I will be watching it in a totally different mindset to everyone else in this thread as I know precisely what happens.
Obviously I have no idea what the film's like but from the book I can't see how people could guess the plot. From the book I guessed something stunk, but it's obvious all the way through, you also realise Chuck's not what he seems as soon as Teddy does, but the actual twist was not what I expected remotely. I thought possibly I had it sussed but I was off the mark.
Then again, I am a person that goes into films and books with no intention of guessing any twist, I don't tend to try and second guess films or books because it takes the fun of out it in my opinion, so maybe I'm the wrong person to ask. I make no effort whatsoever to second guess films, if I ever do it's by accident.