Max Brooks is the Ken Burns of zombie history. In World War Z, a nameless interviewer discusses the experiences of the zombie war with its survivors, and each survivor has a different take on the crisis depending on their occupation, social status, or area of the world they lived. Together, their combined stories create a patchwork showing us the global undead crisis as a whole.
Sounds like a documentary to us. The only difference is that the zombie wars have never happened before and arguably—hopefully!—never will.
Tonally, Brooks shows the same attention to detail of any good documentarian. Just check out Colonel Eliopolis's story and look at all the details Brooks put into Eliopolis's speech to demonstrate her career in the Air Force (6.5). He got all those details by actually going out and interviewing people for the novel. No, there wasn't a secret undead scuffle you weren't told about. Rather, Brooks was doing his research. In his own words:
That was easy for me. The hard part was the research. The irony was that for a book of fake interviews, I had to do just as many real interviews with real people who do those real jobs to get at it. It was almost more a work of journalism than of fiction. (source)
Ever wonder why Michael Choi's description of submersibles seems so real or Todd Wainio's story of being a grunt in a zombie war so realistic? It's probably because there's a real Michael Choi or Todd Wainio out there.