hard back

A hardcover (or hardback or hardbound) is a book bound with rigid protective covers (typically of cardboard covered with cloth, heavy paper), or sometimes leather. They may have flexible sewn spines which allow the book to lay flat on a surface when opened, although most modern commercial hardcover books have glued spines.
Hardcover books are often printed on acid-free paper, and are much more durable than paperbacks, which have flexible, easily damaged paper covers and glued spines. Hardcover books are also more expensive to manufacture and purchase. Hardcovers frequently come with artistic dust jackets. If brisk sales are anticipated, a hardcover edition of a book is typically released first, followed by a "trade" paperback edition (same format as hardcover) the next year. For very popular books these sales cycles may be extended, and followed by a mass market paperback edition typeset in a more compact size and printed on thinner, less durable paper.