Probabilitas?

(We are near the end of November and this is the ninetieth post of the month so it might be the last till December. We have another day long trip from Lancaster to York, for a Winter Fair, scheduled for tomorrow.)

I remember from school that one standard of Classical drama was probabilitas, meaning, in this context, "plausibility" or "credibility" rather than "probability." So how plausible is Poul Anderson's The War Of Two Worlds (New York, 1959)?

The introductory passage makes two significant statements about the "...lord of the Solar System..." (p. 5):

he thinks that Earth is "[a] lovely world...a broad fair planet...one to fight for, to seize and hold like a beloved mate..." (ibid.), whereas the Martians, suffering in thick atmosphere and high gravity, occupy Earth only as a military necessity;

he has a "...great crested head..." (p. 6) whereas the Martians each have only two small antennae (p. 23).

These are early clues that the real controllers of the Solar System are not the natives of Mars and conquerors of Earth. But this is where the plausibility questions begin. A massive, outrageous deception is being perpetrated on an interplanetary scale yet is quite casually penetrated. Then the handful of characters who have learned the truth survive indefinitely as hunted fugitives. Like all good Andersonian heroes, they are able to knock aside the gun of a state trooper and make their escape.

Still, it is always good to see former enemies, in this case Earthmen and Martians, united against a common enemy. Solarians, unite.