Copyright subsists for a variety of lengths in different jurisdictions, with different categories of works and the length it subsists for also depends on whether a work is published or unpublished. In most of the world the default length of copyright for many works is either life of the author plus 50 years, or plus 70 years. Copyright in general always expires at the end of the year concerned, rather than on the exact date of the death of the author. (The right to reclaim a copyright--or "terminate the transfer" of a copyright--commences and ends on the anniversaries of exact dates in the United States.)
So when can one conclude that a book is in the public domain? In the United States, all books and other items published before 1923 have expired copyrights and are in the public domain, and all works created by the U.S. Government, regardless of date, enter the public domain upon their creation. But if the intended exploitation of the book includes publication (or distribution of a film based on the book) outside the U.S., the terms of copyright around the world must be considered. If the author has been dead more than 70 years, the work is in the public domain in most, but not all, countries. In Italy and France, there are wartime extensions that could increase the term by approximately 6 years in Italy and up to about 14 in France. Some works are covered by copyright in Spain for 80 years after the author's death.
