Science fiction is a genre of speculative fiction that is generally based around entertaining but rational alternate realities or possibilities. Despite the crossover with fantasy, science fiction is most different in that the imagined elements are largely held to be possible in accordance with the laws of science – unlike magical and mystic elements of fantasy. Oftentimes a large part of the appeal of science fiction is found in the literary investigation of the effect and consequences of differences or advancements in scientific principles.

Science fiction books are fiction books that are often set in alternative times and worlds, whether it be a distant planet or on Earth in the future or the unknown past. The storylines are frequently based around, or make use of, scientific principles or practises that differ from those in reality – time travel, space travel and radically advanced technology, for example.

Although hard sci-fi normally focuses the story around differences or advancements in the quantitative sciences, soft sci-fi novels are often based around the social sciences; in which key differences between fiction and reality come in the form of alternative psychologies, economics and political sciences. To this extent, George Orwell’s Nineteen Eighty-Four could be considered a work of soft science fiction – albeit of the dystopian subgenre.