Users want their names inscribed on the front cover or want a unique cover customized with images or text they choose. Publishers offer users a choice of covers for the book. Publishers offer users the option to pick and choose which parts of the books they want to print. If the book is a reference book, users might only want to buy specific chapters. Publishers offer to combine college text book with class lecture notes and materials, which are often referred to as course packs.
Users pay the authors to add unique content to books specifically written for the customers.
For example, a customer might buy a motivational book for her company and ask that the book be printed with a chapter on the company's history. Many people were familiar with the concept of books on demand. I assumed everyone was familiar with the technology that enables a single book to be printed, economically and quickly, from a digital printer. But many of the people I spoke with assumed all books were still printed in large quantities on offset printers with ink and not on digital printers with toner. The idea that it is possible to print a single book with quality that matches offset printing was quite surprising to many people.