The series was written over a span of more than five decades. It totals four million words across nearly 10,000 pages, with two further books in production at the time of the authors' deaths. In the first volume ("Our Oriental Heritage", which covers the history of the Middle East and Orient to 1933), Will Durant stated that he wanted to include the history of the West to the early 20th century. However, the series ends with "The Age of Napoleon" because the Durants both died—she in her 80s and he in his 90s—before they could complete additional volumes. They also left behind notes for a 12th volume, "The Age of Darwin", and an outline for a 13th, "The Age of Einstein", which would have taken "The Story of Civilization" to 1945.