Lester del Rey 
World of Science Fiction, 1926-1976 [PDF ebook] 
The History of a Subculture

This book, first published in 1980, is a guide to the major forces in the subculture of science fiction. It analyses the history of the field and the related developments, for instance the Bomb, that have shaped the literature. It examines the complex of activity and background tradition, the body of accepted beliefs and conventions, and the ethics and values of the world of science fiction.