David Levithan and Andrea Cremer met each other in Washington, DC, even though that's not where they live. Andrea was pretty certain she wasn't invisible, but David confirmed that fact by introducing her to some other writers, who were all able to see her.
Before writing with Andrea, David had never written a novel with a one-word title. His novels include Every Day, Will Grayson, Will Grayson (with John Green) and Nick & Norah's Infinite Playlist (with Rachel Cohn).
