A publisher will usually create a print run of a fixed number of copies of a new book. These books can be ordered in bulk by booksellers, and when all the bookseller's copies are sold, the bookseller has the option to order additional copies. If the initial print run sells out quickly, the publisher will probably have more copies printed. When the book is no longer selling at a rate fast enough to pay for the inventory costs, the publisher will cease to print additional copies, and may remainder or pulp the remaining unsold copies. When all of the books in a print run are sold to booksellers, the book is said to be "out of print", meaning that a bookseller cannot get any further copies from the publisher. If a book sells surprisingly quickly, a book may be out of print briefly when its initial print run is exhausted, but soon reprinted.
A reader who wishes to purchase an out of print book must either find a bookseller that still has a copy, wait for another print run (if another is anticipated), or find someone who will sell their own copy as a used book. The advent of the Internet has made this process much easier, as many websites sell rare used books.
Some publishers intentionally limit the print run of some or all titles to fewer copies than the anticipated demand, in creating limited editions marketed to collectors. In these cases, there is an implicit or explicit promise to collectors that the book will not be reprinted, at least in the same form as originally published. For instance, Madonna's Sex was sold in an sealed envelope and it is, according to BookFinder.com, the most sought after out of print book in the US. BookFinder.com releases every year the BookFinder.com Report, a list of the most sought after out of print books in the US.
The longer a book has been out of print, the more difficult it may be to obtain a copy. If there is enough demand for an out of print book, and all copyright issues can be resolved, another publisher may republish the book with a new cover and title page. In some cases, an out-of-print book, even one that sold very poorly, may be republished if the author becomes popular.
In the United States, the Thor Power Tool decision (1979), by limiting the circumstances under which publishers can take a loss on their inventory for tax purposes, has probably caused some books to go out of print more quickly than they otherwise would.