10 Works of Literature That Were Really Hard to Write

"Joyce was nearly blind, so he dictated his stream-of-consciousness prose to his friend, Samuel Beckett. That led to some unexpected results. For example, during one session, Joyce heard a knock at the door, which was too quiet for Beckett to perceive. Joyce yelled to the visitor, “Come in!” so Beckett added “Come in!” to the manuscript. When Beckett later read the passage back to Joyce, the author decided that he liked it better that way."

http://www.mentalfloss.com/blogs/archives/76496