On occasion Charles Darwin can seem our scientific contemporary, for the subjects he engaged remain engaging today, but in his role as author he belongs to the past. It is not customary today for scientists to write book after book, as Darwin did, or for these books to serve as the primary vehicle of scientific communication. For Darwin, however, the book was central. He wrote at least eighteen, depending on what one counts; in his Autobiography he entitled the section describing his most important work ‘An account how several books arose’; and in his personal Journal, begun in August 1838 after he had come to a mature sense of himself, he organized entries around his books. A characteristic entry is that for 1846: ‘Oct. 1st. Finished last proof of my Geolog. Observ. on S. America; This volume, including Paper in Geolog. Journal on the Falkland Islands took me 18 & 1/2 months:–’. Further, almost always he had a book under way: when one was complete, the next was begun. He called them the milestones to his life.