Ok, I learned this at a bar, and once you hear this you'll understand why no women gravitated to our little group of publishing wonks. We were talking about...drumroll...check digits! Yes, the ISBN check digit. Ok, we did discuss other things, but this is what has stuck with me and the young sprout who clued me into how it's calculated pointed me in the direction of Wikipedia and the full story of isbn's. I am giddy with knowledge this AM.