It struck me a bit odd to see Nevil Shute's On the Beach (which I loved) on a SF/Fantasy list. I always put it in that Cold War "what if they push the button" genre along with Failsafe, Red Alert, etc. Never really thought of it as SF.

And I dunno about Starship Troopers as a second choice for Heinlein. I'd have to go with Time Enough for Love, which I think belongs on the list anyway. I can think of other Heinleins I'd replace Starship Troopers with...The Time Tunnel for one.