Some books were never meant to be movies. Personally, I think that World War Z is one of them. This movie version can't really be taken as evidence either way, since it bears so little resemblance to the source material, but perhaps that in itself is evidence against it. I think the filmmakers gave up trying to replicate the book and just made another generic zombie film.
There is no one hero in Max Brooks's book. The narrator tells the stories of people that stand out in his research, and some of them had crucial parts to play in the war, but really the protagonist of every story in the book is a hero, just for having survived the war. The stories come from all over the world, and are about people of all kinds, giving the book a richness and complexity that immerses the reader in what is happening. The lack of a central character makes the book more realistic, since if there were a zombie outbreak, there would be no shining savior, just humanity as a whole trying to survive. In contrast, the movie implies that Brad Pitt's American white man is the only one who can save the world. And it's clear that there's no way that all the stories from the book could fit into the movie anyway, since that would make for a multi-part movie that would put Peter Jackson to shame.
What also made the book fascinating was the way that it revealed truths about the world through the various responses to the zombie outbreak, from the government level down to the individual psyche. That social commentary is lacking from the movie, making it just another CGI-laden zombie action flick.
But let's forget for the moment that this was supposed to be based on a book. As far as CGI-laden zombie action flicks go, how was this one? Good enough, I suppose. The action is fairly unrelenting, and the acting is good. A common pitfall in movies like these is that characters will often behave with no common sense, or the zombies will act in unrealistic ways. This movie avoids that for the most part, although not completely. And the CGI is fine, although I will never be a fan of fast zombies. I think that if zombies actually were fast like that, it would be all over for humanity very shortly.
But when it comes down to it, this movie really has not much new to offer. It will hold your attention for a short time, but it's devoid of the spark that made the World War Z book what it was. A friend of mine suggested that the book would have been better done as a mini-series, and that's actually not a bad idea. Just make the zombies slow, please.