Another theme could be survival. In many science fiction stories, characters face difficult situations and have to fight to survive, and this ebook might be no exception. There could be threats from alien species, harsh environments, or malfunctioning technology. Also, the theme of identity could be present. With the advanced technologies often featured in science fiction, characters may question who they are or what it means to be human. For example, if there are cyborgs or clones in the stories, they might struggle with their sense of self.
One possible theme could be exploration. Since it's science fiction, it might involve exploring new planets or uncharted regions of space.