The real point I want to get into is how it was a very poor adaptation of the book, like adaptation in name only. The book is about societal collapse and eventually, its reconstruction. It’s accepted that the zombie plague can’t be cured, can’t be prevented, and is always fatal. Conventional methods of warfare are ineffective. Ruthless, amoral methods end up being the only way to survive, from cannibalism to using humans as zombie bait.
The movie shows none of that, except maybe the plague being incurable. Zombies are unstoppable excepting headshots, like in the book, but there is never any modification of tactics beyond that “infect yourself with a curable disease and then the zombies won’t want you” thing. Even though I would think that the rotting undead wouldn’t be that picky. Seeing as they’re dead.
But that’s beside the point. The movie is weak. The societal upheaval is replaced with a man searching for clues about the disease so he can reunite with his family. Granted, the original framing of WORLD WAR Z had no main character (except maybe the guy conducting the interviews), but still. They could have come up with something better than the weaksauce every-action-movie-ever plot they had. They didn’t try to make a WORLD WAR Z movie (or they tried and failed…miserably). They made a zombie movie with World War Z as its title.
Finally, I would like to point out that just because this movie of a book was bad doesn’t mean all book-movies are bad, even the ones that are bad adaptations. The original version of Blade Runner is hardly the adaptation of Do Androids Dream of Electric Sheep? but most consider it a good movie in its own right. So if you’re not going to make a good adaptation, at least try to make a good movie.