In the book, there was a bit of a twist in the story (at the end, of course). The trailer appears to show the twist as being the main plot of the movie. If so,then the movie makers didn’t understand the book at all.
Card, heavily involved in the film of his story, took a different take on it. The book’s “McGuffin” was the twist at the last “game”; there will be a different one for the film.
No, I don’t know what it is :)
We’ll have to see the film :D