Books are different from other goods because

This passage sums up the problems peculiar to the book trade make it different from any other trade-the problem of selection and the problem of sticking. How is the bookseller to tell what, in an enormous output, will prove sale-able before the full weight of unsold items affects the balance of his business and how is he at the same time to hold a stock large enough to enable the public to choose freely? He may seek to escape from this dilemma by becoming the passive sales representative of large publishing houses or distribution networks but he is then no longer a book seller. He may take refuge in the sale of items to a restricted circle of customers but he thereby cuts himself of from all that is vital in his trade and dooms himself to mediocrity and stagnation. On the other hand, he may protect his business from the danger of idle stock by speculating on the latest publication but this is a dangerous game in that it implies a constantly changing clientele: readers remain faithful to their own discoveries and failure to follow up a book an author or a type of literature means dismissing the public responsible for their success.
This brings us back to the fact that books are indefinable. The story is told of a certain country with a great many generals where it was decided to present a rare and valuable edition of an old book to a general about to retire. The old soldier looked at the volume and remarked, ‘A book? What’s the point? I’ve already got one!’