Not just that, but only one person can have the book at any one time - unlike our current piracy system where one copy can spawn effectively infinite sub-copies

Not just that, but only one person can have the book at any one time - unlike our current piracy system where one copy can spawn effectively infinite sub-copies. This means that when a given number of people want to read a book (and particularly if they want to read it in some relatively short period after the book's release), you need to have a substantial number of new book sales to support all those people. This isn't a requirement with modern-day piracy.