Well, it seems there is no rest for the wicked! My publisher has just sent me an email asking whether I'd be available to write some course notes for one of the American game schools. They're using the book in one university on their porting course, and want some notes to aid the other 18 campuses.
By my reckoning that's a lot of students. Each buying a book. Every year.
Ok - so it won't happen like that, but I'm interested to see how the sales are affected, or not, by this.