My new non-fiction book, Science Fiction of the 20th Century , had a lot to cover. It's an enormous field. You can cover the paperbacks, the movies, the hardbacks, and the magazines, and think you've got it. You don't have it, not nearly. It's too damn diverse.
Writing styles are too different, and what they cover is too different.
It's very difficult for me to summarize all this in my book. The only way I could do it was in broad outline, and then anecdotally. Fortunately, in one respect, I'm one of the few writers in the field who did his apprenticeship at Ziff-Davis, did the longest professional interviews with Clarke, with Heinlein. But the very best science fiction urges the reader to speculate. Because of its nature, it appeals to a younger audience.