Remaindered books are books that are no longer selling well and whose remaining unsold copies are being liquidated by the publisher at greatly reduced prices. While the publisher takes a loss on the sales of these books, they're able to make some money off the sale and clear out space in the warehouses.

Copies of remaindered books are marked by the publisher, distributor or bookseller, to prevent them from being returned. "Remainder marks" have varied over the years, but today most remainders are marked with a stroke with a felt-tipped marker across the top or bottom of the book's pages, near the spine.

Only hardcover

Hardcover

A hardcover, hardback or hardbound is a book bound with rigid protective covers...

s and trade paperbacks (paperback books, often larger than "pocket" paperbacks, sold "to the trade" or directly to sales outlets) are typically remaindered. Mass market paperbacks ("pocket" paperback books sold through a third-party distributor) usually become stripped book

Stripped book

A stripped book is a mass market paperback that has been stripped of its cover in order to be pulped and recycled as a result of lack of sales...

s rather than remaindered books. A book that might retail for $20 will typically be purchased by someone specializing in remainders for $1 and resold for approximately $5.

Remaindered books in the United States

Since the Thor Power Tool Company v. Commissioner of Internal Revenue decision of 1979 in the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

and its adverse effects on the keeping of inventories for several years, books in the United States have been remaindered much earlier and in greater quantities than prior to the decision. Since that 1979 decision, the number of unsold books which have simply been destroyed (by being burned or recycled into paper or cardboard) instead of being sold at a large reduction has also risen greatly.