Conclusion
In the end, the author photo plays a mostly subtle roll in the cycle of written to published to purchased and read. Over time it has gone from a mark of note, signifying some great literary prowess, to a common place staple of many books. It's so all consuming that it is more noticeable when there is no picture, which can be its own kind of marketing, driving people to go that next step and search for more information about the book. But either way, whether an engraving in the 1600's or a professionally composed full-color headshot on a shiny new paperback, the point of the author photo is to try and create additional demand for the book. With a single photo an author can be a friend, an enemy, a teacher, someone to lead you from the straight and narrow, or someone to set you right. But at the end of the day, authors write, and what is written needs to be read by somebody. The author photo is just one more step between Point A and Point B. Everybody wins.