Noted critics and authors write on various aspects of science fiction
as a genre. Kingslay Amis identifies the roots of modern sci-fi in
Shakespeare; Stanislaw Lem discusses some of the logical implications
of time travel stories as employed by Bradbury, Heinlein, Frederic
Brown and others; while CS Lewis considers the various categories of
science fiction & Darko Suvin presents a comprehensive discussion
of how sci-fi works.