Q: What was the specific writing process like?
I wrote chapter one while David was writing chapter two. Then we met at my apartment in New York City and read our chapters out loud to each other. (Sarah was also listening.)
After the first chapters, we were convinced we could turn the thing into a book. I wrote chapter three while David wrote chapter four, and then we met to read those aloud to each other. This process continued over more than a year. We discussed plot occasionally—especially the stuff that happened with the two Wills together—and we discussed the overall shape of the novel (we wanted it to be shaped like an X), but mostly we just read to each other and then kept going.
I don’t think I actually saw David’s text until the first draft was finished. It really was a story made to be read aloud (the audiobook, incidentally, is fantastic), and although there were years of revision working to make the story cohesive, we had a hell of a lot of fun making it.