The science fiction genre encompasses many sub-genres including apocalyptic, time travel, and space opera. Science and technology are usually central to the story, no matter the sub-genre, and there are standard elements that sci-fi readers expect. Author Nancy J. Cohen's first series of novels, The Light-Years, are sci-fi romances that are set on other planets. While these stories are driven by romance and relationships, there are also aliens and space travel. Cohen then wrote several books where she explored setting the stories on Earth with heroines that come from outer space, along with some elements of mythology and paranormal romance. A lot of different elements can go into science fiction stories, she says. The science fiction category as a whole has a very dedicated readership, but some of the subgenres have to find their niche. Cohen encourages writers to explore the facets of science fiction, as all of the self-publishing options for eBooks continue to provide authors and readers the opportunity to connect.