BOOKS AND FILM are different mediums; what works in one rarely works in the other. Still, it's hard to read World War Z by Max Brooks—Chronicler of the Undead, Son of Mel—and not see how a film version could've worked. Subtitled "an oral history of the zombie war," Brooks' post-apocalyptic survey profiles the war-weary survivors of a global zombie infestation, turning out to be less about zombies and more about Middle Eastern politics (Israel, sensing danger, is the first to put up a protective wall), international trade (it's through smuggling and human trafficking that the infestation spreads), and America's tectonic class disparities (guess who's better at rebooting society: internet-reliant off-ice drones or migrant workers?). Relevant and scary and melancholy, Brooks' book pushes all the right buttons; with a few million and a few hours, Ken Burns could've turned it into something remarkable.

Instead, we get World War Z, which—as a wannabe action franchise and a multiplex-friendly narrative—ditches nearly everything interesting about Brooks' book. Brad Pitt plays Gerry Lane, a U.N. investigator who's assigned to find the source of the zombie outbreak. These frenzied, milky-eyed monsters are world-class sprinters, and the speed with which they spread—swarming like ants, gruesomely popping and locking, chattering their teeth like they're really cold—is responsible for the film's too-few thrills: a solid opening finds Lane and his family stuck in an ordinary Pittsburgh traffic jam, and it only takes a few impressive, convincing moments for everything to go straight to shit.

But it's downhill from there, with Lane visiting devastated locations—South Korea! Israel! New Jersey, which looks pretty much the same!—and having things that aren't quite adventures. Pitt isn't to blame, but rather Marc Forster's tepid direction (he somehow manages to drain the intensity out of a zombie attack on an airplane) and a devolving, shuffling script. Literally and figuratively bloodless, World War Z isn't scary, and it isn't fun, and its CG spectacle is a poor substitute for Brooks' ambition. Maybe somewhere down the line, somebody will give Ken Burns a call.