A growing number of authors and publishers freely distribute their books electronically to increase the visibility of their work. These books, for both academic and general audiences, cover a wide variety of genres, including technology, law, fantasy, and science fiction. Some authors claim that free digital distribution has increased the impact of their work and their reputations as authors. But beyond increased exposure, a vital question for those with a commercial stake in selling books is, “What happens to book sales if digital versions are given away?”