Print-on-demand publishing is a growing segment of today's book market.
For the uninitiated, print-on-demand means that books are printed as they are ordered rather than having a fixed print run of ten, twenty or thirty thousand books. For publishers, not having to commit money and warehousing space to thousands of books means we can take chances on new authors.  
In the early days, print-on-demand technology wasn't great - the text wasn't even and the bindings often fell apart. This is no longer the case and I believe the average book buyer would struggle to tell the difference between a book printed as part of a mass print run and a book printed as needed. Many academic publishers use only print-on-demand as it saves on storage and avoids making a commitment to titles that might sell in hundreds rather than thousands.
So while quality has improved, there is still a reluctance among book sellers to stock print-on-demand titles. They say they can't return them if the books go unsold. I have clarified this with our printer, who say that book sellers can return unsold books just as they can return other traditional mass-produced titles. The ruffle may come from the distributors who carry books between printer and shop - this very traditional segment of the industry do not want to carry unsold titles back to the printer.
So book sellers, as the industry moves forward into the digital age, and printing to order becomes the way of the future, we must figure out how to adapt. I am happy to bypass the distributor. Order from us direct, 0845 116 1476, and we will take back our unsold titles. I assure you.