Having read the book World War Z, I could tell from the trailers for this movie that it wouldn't exactly be a faithful adaptation. I thought that the most interesting aspects of the book were its exploration of how the Zombie plague affected social and political structures across the world. Anything like that is completely ignored in the film, but I can at least understand how the filmmakers thought that those aspects wouldn't work in a single feature length movie. What I can't understand is how the filmmakers seemingly ignored the book's most obviously cinematic content. The book features a lot of setpiece action scenes, and to be fair, many of these involve world cities falling to zombie infestation and the movie does do enough to cover this. However, the book's immense battle scenes - the meat of the titular Zombie War, such as the Battle of Yonkers, nuclear war between Pakistan and Iran, Chinese civil war and massive formation combat against zombies - are completely absent. I was very surprised that they did not cover these, especially the Yonkers scene, because they would obviously fit so well into a film and the script, even as it is now, could easily be tweaked to include or at least mention them. The action that did make it into this film is very unsatisfying and obscure thanks to the restrictions of the PG-13 rating, and the narrative around is not engaging enough to really get me invested in it.
I was also surprised at how cheap this movie looked. This film cost hundreds of millions of dollars to make, but it's hard to see where it all went on the screen. Swarms of zombies look very fake and nonthreatening, and in some cases individual zombies are computer animated, which gave me bad flashbacks to I Am Legend's awful CGI overload. Aside from the opening scenes in Philadelphia and the middle act in Jerusalem, there are no big outdoor sets. A South Korean airbase is portrayed as a series of dark rooms; too much of the movie takes place in an airline seat; there is a lot of sitting around inside of the aircraft carrier, etc. The sense of scale is very inconsistent, and this is accentuated in the bizarre final act, which was obviously the focus of the infamous reshoots as it feels like a completely separate movie. I consider myself a patient viewer, but this very long and dull scene started to bring me down after a while, and my less patient viewing audience eventually fell completely out of sync with the film and began to make fun of it at every opportunity - not really a fair criticism of the film, but it's a real issue when it can't hold an audience's attention. The final act does actually have an interesting idea at its heart, albeit one that completely doesn't connect with anything in the book, but I just didn't think it was a well executed concept. The very different style and tone of these scenes makes it feel like a completely different movie.
Again, while there was nothing all that terrible about WWZ, I didn't think it was anything to get excited about. In other words, a perfect 5/10 movie. I wish they were more aware of the source material's potential because without the best and most cinematic aspects of the book, WWZ (the film)and WWZ (the book) only share a title and the central premise of a zombie plague, which is not an original idea in itself.