even before the World Wide Web came into existence
Actually it was around, and even web pages existed. Although they were all simple html code. However, to buy the wonderful Ebook would have been challenging:
1. Login via a 56Kps phone modem. Noisy phone lines throwing garbage on the screen. Aah the good ole days.
2. No search engines till the mid 1990s. Which means finding the page where he advertised his Ebook would mean one already had the addr of his webpage.
3. Then to buy something, there were no secure encrypted software for credit cards. A hacker's dream world.
So yes the daddy of CEO Porter could've sold his Ebooks. Assuming Ebooks existed. But it sort of has a different ring to what occurs today.