I guess if you know the book, you already know not to expect anything along the lines of Narnia or Alice in Wonderland, because the movie is pretty faithful to the book. It's just not the movie that the marketers are telling us we're going to see.
SCIFI.com interviews the director and one of the producers in the link above, so you should go read that. The director is a little upset that the movie he made isn't the one that's being advertised. The producer, on the other hand, is more pragmatic. "As a producer I can explain it in simple monetary terms: If you need honey, get a bear. And I can tell you if everyone who read the book brought three friends, then it would still lose money." He goes on to say, "Everyone who read the book and sees the trailer says, 'What is this? This is nothing like the book. What are you doing, Dave?' And I say, 'You know what you're seeing is 15 seconds of a 90-minute film. Give me a little leeway and respect. Go see it, and then tell me what you think.'"
Well, of course he'd like for folks to go see it. He just got finished justifying the fact that the ad campaign misleads audiences in order to trick them into seeing a different movie than they're paying for. It's like he's saying, "Hey, Harry Potter fans! Have I got a movie for you! Come and see!" Then he turns to the folks who prefer the quieter story of a couple of kids trying to escape being bullied at school and whispers, "Don't worry. It's not that kind of movie at all. It's really the movie that you want." He's trying to have it both ways and while I understand his point-of-view, I don't get the part where folks are supposed to "respect" him.
Having said all that, I might still be interested in seeing the movie, but I'd like to see a more accurate trailer to help me make up my mind.