post referred to one work each by Wells and Hoyle, two by Anderson and several by Stirling. Because of the reference to Hoyle's October The First Is Too Late, I have started to reread it. Hoyle makes the point that an sf alien should be something other than a human brain in a reptile body or even a humanoid body. Perhaps Anderson's Merseians or Ythrians measure up to Hoyle's criteria?
Wells and Stapledon: Martians invade Earth;
Stapledon: Earthmen invade Venus and Neptune;
Lewis: a demonically possessed scientist from Earth mounts a moral attack on the sinless Venus;
Hoyle: an intelligent gas cloud enters the Solar System;
Anderson: Martians conquer Earth but are controlled by extra-solars;
Anderson: militarily superior extra-solars conquer Earth economically.
Wells: The Time Machine;
Stapledon: mental time travel;
Lewis: an argument that physical time travel is impossible;
Hoyle: serious discussions of the significance of time and the meaning of consciousness;
Anderson: the Time Patrol etc.
Thus, a powerful tradition of serious speculative fiction.