I think that when you adapt a popular book into a movie, the first teaser has to be geared towards fans of the book to get them on board, to show that you respect the material. That was the case for the first teasers for Harry Potter, Twilight, and The Hunger Games. And that appears to be the case for Ender's Game.
But that doesn't do a lot for those unfamiliar with the book. It leaves more questions than answers. It looks interesting, but I need to see a lot more before I'm sold.