Last week I attended the Haverhill Public Library's annual book signing and sale. About 50 local authors attended. And about 20 visitors. Based on my experience with promotional events — for example, the 1997 Las Vegas InterOp tradeshow — this seemed a little slow. But according to the other authors, this year's turnout was great. "Better than last year."

I arrived with 18 books in my box. That's all I had left and my new order hadn't arrived yet. I was pretty nervous, thinking that I might...