I am currently in the midst of reading Rant: An Oral Biography of Buster Casey, by Chuck Palahniuk. This is the second book that I have read in the last year that utilizes the oral history format. The first one was World War Z: An Oral History of the Zombie War by Max Brooks (which advocates the “classic” slow zombie, by the way). In fiction, the format is presented as the recollections of the story’s characters as told to one focal person, who may or may not also be a “true” character in the book.
At first, I thought this would be a boon for the writer. When you get stuck, just switch to a different character! However, upon further reflection, I think to pull it off well actually requires much more calculation than my first flippant view implies. Each character’s viewpoint and especially their knowledge of the described events have to be kept discrete, allowing the story to unfold as the reader pieces the scraps together to form a complete picture.
As far as adaptation to a screenplay, I see some particular obstacles. Since the format relates events that have already happened, a straight adaptation would likely turn into the to-be-avoided “talking heads on screen”. I have read that the screenplay for World War Z is currently being written. My guess is that the filmed version will not follow the multiple interviewee format of the book and will likely be a straight-up action flick, weaving elements of the book into a linear storyline, perhaps with a single survivor reminiscing the entirety.
I will be on the lookout for films adapted from the oral history format to see how the writers maneuvered to bring the story to the screen.