It strays from genre conventions however due to its massive scope and the way in which the story is told. In World War Z, each chapter serves as a separate interview (conducted by the author himself) with different individuals across the world who play all sorts of roles in the global Z War. They range from a soccer-mom mayor in Montana, to an astronaut on the International Space Station, to an officer of the Korean Intelligence Agency. And from the moment the story starts, Brooks creates this facade that the book you're reading is a collection of accounts created after the war, which itself was very real, and absolutely devastating. The story is typically told with extraordinary detail and is written in a way that events unfold in a plausible and realistic manner. This is no Dawn of the Dead, where the survivors are isolated in a mall with a conveniently placed gun shop and endless supply of food. Instead, the few survivors must dangerously scavenge for food, struggle to keep their cities alive or retreat, and eventually build their own sort of war-economy as their prepare to fight back en masse for the first time.
It's difficult to say what it is about zombies that allows the genre to continue to survive over the years. Being a destroyed version of humanity, their mindlessness and destructive nature reminds the audience what humanity may very well succumb to if they give into complacency. The zombie symbolizes a human who has completely lost his individuality and become one of many who has mindlessly given in to the world around them. Yet they selfishly only think about their own survival, meanwhile mankind is composed of individuals who must band together in World War Z and think selflessly before they are able to successfully defend themselves and survive.