I know you asked for sales books, but I haven't really read many of those. (biggerpockets.com)
Example # 1: In the traditional publisher model the advance for a 10,000 sale book in trade paperback would be about $ 15,000 for basic rights tied up for at least a decade. (deanwesleysmith.com)
«Best sales book ever,» is what some people are saying about this book. (amazon.com)