So - fast-paced action. Don't think too hard about the science here. First of all, it's 1931, we didn't know as much back then about the solar system or energy generation and certainly about space travel of any sort. There are violations of the conservation of energy, and we now know that the moons of Jupiter are much more numerous and aren't anything like what's depicted here. Now, he did get it correct that moving such a moon out of its present orbit will be disruptive to the rest of the system, but I'm pretty sure not nearly as much, or as suddenly as depicted here.
LOTS of cliches, racial stereotyping, humanoid "aliens", and caricatures of damsels in distress - well, caricatures by our current standards. I alternated between laughing and being offended at times.
Still, as with any quality SF, there were some interesting ideas there. The copper-clad world refers to a world/moon entirely enclosed in a shell, like a Dyson sphere except it surrounds a rocky body instead of a star. I doubt copper would be the ideal material for such a shell but i guess it sounded too cool not to use. There is some notion of using nuclear power sources but poorly expressed... probably because nuclear power was only theoretical at the time. This was published 7 years before the discovery of nuclear fission and 11 years before the first atomic pile and controlled chain reaction.
Unfortunately, the characters are not particularly well developed or plausible as people - which is sort of typical of the space opera genre. The "heroine", in particular, was a cardboard cliche of clinging desperation and hero-worship of "my Carson"
with the hero apparently admiring the girl's courage in draping herself over a perfect stranger from another planet and professing love. Bad guys are ugly, good guys are good looking. Very black hat/white hat in approach.If you've only known space opera from parodies this is your opportunity to see the real deal. Not as good as the Lensmen series by EE Doc Smith, but then, there's a reason Lensmen is considered a classic. A lot shorter, though.
