Science Fiction has proved notoriously difficult to define. It has been explained as a combination of romance, science and prophecy; as a genre based on an imagined alternative to the reader's environment; and as a form of fantastic fiction and historical literature. It has also been argued that science fiction narratives are the most engaged, socially relevant, and responsive to the modern technological environment. This Very Short Introduction doesn't offer a history of science fiction, but instead ties examples of science fiction to different historical moments, in order to demonstrate how science fiction has evolved over time. David Seed looks not only at literature, but also at drama and poetry, as well as film. Examining recurrent themes in science fiction he looks at voyages into space, the concept of the alien and alternative social identities, the role of technology in science fiction, and its relation to time — in the past, present, and future.