This is essentially everything I would have said on the subject. Python 3 is technically very good, but no one is using it, hence no commercial interest in the book. The optimist would say it was just ahead of its time. The pessimist would say Python 3 is a dead end and I backed the wrong horse. I'd say the jury is still out.
He discusses "earning out" on a recent post from his blog[1]:
> The book went on sale in mid-August and earned out almost immediately. “Earning out” is a publishing term which means that the book has sold enough copies that my cut of the profits has paid back the advance payments that O’Reilly gave me during the writing process. Which means that I’m already receiving royalty checks for real money.