Personalities don't get much bigger than Robert Heinlein and Isaac Asimov, two giants of the genre. Though their views often clashed, the two spoke throughout their lives; they first met when Heinlein got Asimov a job at a Philadelphia Naval Shipyard. Primarily their conflict became a political disagreement, as Asimov revealed in his posthumous 1994 autobiography. Read on for the SF burn from beyond the grave.Living longer than Heinlein allowed Asimov to have the last word in the debate, bashing the release of Heinlein letters Grumbles from the Grave. After sneeringly jabbing Heinlein for making editor John W. Campbell never reject one of his stories, he says:

Furthermore, although a flaming liberal during the war, Heinlein became a rock-ribbed far right conservative immediately afterward. This happened at just the time he changed wives from a liberal woman, Leslyn, to a rock-ribbed far-right conservative woman, Virginia.

Asimov's favorite Heinlein novel was Double Star, an appraisal echoed by critics like James Blish. He did not like the way Heinlein tried to subtly alter his work for the period he was writing in:

Heinlein, on the other hand, tried to keep up with the times, so that his later novels were "with it" as far as post-1960s literary fashions were concerned. I say "tried" because I think he failed.

The contemporary reader can be forgiven for assuming "rock-ribbed" is a metaphor for the unprotected sex a right-winger would presumably endorse. It does after all mean "firm and unyielding."