I suspect that [Heinlein's] most enduring work will turn out to be the dozen juvenile novels he wrote for Scribner's after the war.

Juvenile science fiction, as a labeled category, begins with Heinlein—though in fact most of the earlier magazine science fiction had been written for youthful readers and censored of anything likely to give offense. There had been new inventions, too, in Tom Swift and the dime novels, but no real futurology. The Heinlein series was a pioneer effort, quickly imitated….

Based on solidly logical extrapolations of future technology and future human history, [the novels] are cleanly constructed and deftly written, without the digressions and the preaching that often weaken the drama in his later work.

What I most admire about them is Heinlein's dogged faith in us and our destiny. No blind optimist, he is very much aware of evil days to come. His future...