The most popular book I've seen used as a topic for essay 3 so far this year is....(drum roll)....
Obviously, it's still early in reading season, so my "Book of the Year" may change, but it seems as though this bit of existentialism is being served up quite routinely in AP English classes this year. There have been some fantastic essays in which students have talked about how this book affected them and how they act. Of course, there have been plenty of essays that read like a book report, summarizing the plot.
I'm personally enthralled by absurdists like Camus, Ionesco, and BĂ©renger ( and other French writers like Sartre and Hugo), so it's been fun for me to read your "take" on this one.