From 2016: The history of the Dummies Guides
... But talk to Dan Gookin, who wrote DOS for Dummies, and you get a saltier version. “There was a lot of ego involved, and a lot of petty bullshit that always happens when you have something that’s a success,” he told me from Coeur d’Alene, Idaho, where he is a city councilman. “They would have wrapped that title around newsprint and it still would have sold.”
https://slate.com/culture/2016/04/the-history-and-delights-of-the-for-dummies-how-to-books.html