For physical books, the links go straight to the “buy” page at Publishers Graphics, where the books are printed in response to orders and shipped directly from there.
The PDF links go straight to the “buy” page at the Gaming Un-Store, with Paypal links from there. If you want to read more about the games, then use the menu to the left. Also! All book sales include the PDF for no extra charge.
Book orders require the customer to pay shipping costs. PDF orders are fulfilled manually and are subject to minor delays.