I get the impression that most or all of his sales were due to the "controversy" surrounding the C&D letter from Jack Daniels. He got a bunch of short-term publicity from that, and the book's popularity faded along with the media hype. Maybe he assumed that once it was on the bestseller list the sales would just keep rolling in, but that clearly wasn't the case. It seems misguided for him to blame Amazon for that, when it's possible that readers just didn't find the book appealing.