Self-publishing is a pretty tough game for most authors, but as the industry matures and best practices start to emerge, we’re starting to learn more about what makes a self-published title sell.

Each year, Smashwords parses its sales data to give the rest of the world a little glimpse into what works for its best-selling authors. To absolutely nobody’s surprise, the fifth annual survey revealed that romance, erotica, and young adult fiction are the top sellers for the digital self-publishing...