An out-of-print book is a book that is no longer being published. The vast majority of all books published since the invention of the Gutenberg Press are out-of-print. However, copies of out-of-print titles can still be purchased thanks to the used book business. Walk into any secondhand bookshop and you will discover countless out-of-print titles. The most famous out-of-print book of modern times is Madonna's Sex book. The author does not wish to republish the book so collectors are limited to the original editions.