As you've seen from the trailers, Brad Pitt's big screen adaptation of Max Brook's World War Z doesn't really represent the book at all. The one thing it has in common is that it includes zombies, but even the zombies aren't the zombies from the book. In the book they are slow, but in the movie they are a crazy fast swarm. In a recent interview with EW, Pitt explains why they ditched the slow zombies saying,
The book focused on slow zombies. We chose to be more dynamic in that we wanted to base all of this on science. So it’s ‘What if we had them move like ants? Or a swarm of bees? Or birds or a school of fish that’s being chased?’ One of the first [questions] we asked was how to portray the zombies and how to do it differently because it’s been done so many times and been done pretty damn well.
You can't really argue with him; they did come up with a genuinely unique style of zombie that's sure to be entertaining to watch. Hopefully the special effect can hold up throughout the entire movie. Even though the movie isn't really World War Z, it still looks like it's going to be an entertaining zombie flick.