If you clicked through, it went to the author's website where you could register to be notified when the book came out. My assumption is that he was trying to show his publisher that there was interest. It's been awhile, but I did sign up for the notification, so I think it must have been financial in nature.
"Let me offer you my definition of social justice: I keep what I earn and you keep what you earn. Do you disagree? Well then tell me how much of what I earn belongs to you - and why?” ~Walter Williams