I think
The Sky People Venus is not a matter of bogus science, but rather what is and what isn't.
I think terraforming a planet is certainly possible, and populating it with dinosaurs and humans is also possible, it hasn't happened, but it certainly could have if the past was different.
Another Pulp Book
The Seas of Venus by David Drake is an interesting contrast:
Earth is a dead cinder beyond the dense clouds. On a terraformed Venus the land is ruled by savage plants and beasts, while monsters out of nightmare swim through the globe-girdling seas. Mankind huddles in domed underwater Keeps, living a purposeless static existence dedicated to pleasure, and destined for oblivion later if not sooner.
Only the Free Companions, the mercenaries who fight proxy wars for the Keeps, live on the surface of Venus. They live till they die with the searing thrill of danger, and their deeds bring excitement to the bored residents of the Keeps; but Mankind is doomed unless something changes.
Few are willing to risk their lives for that change, battling both the terrifying environment and the ruthless oligarchs living their lives of luxury. But there are a handful of courageous visionaries in the Keeps and in the Free Companies where death is a way of life!
The Venus Henry Kuttner and C.L. Moore described in Clash by Night and Fury was among the most vivid creations to appear in Astounding Science Fiction during the greatest years of that magazine. Here David Drake revisits their world with two novels as colorful and imaginative as the originals
SURFACE ACTION
Johnnie Gordon was born to wealth and privilege in the Keeps, but his whole life has been dedicated to becoming a warrior of the Free Companies like his uncle. Now his chance has come - a deadly struggle through hellish jungle to steal the enemy's most powerful battleship. If Johnnie succeeds, then one more duty awaits him: a duty that will haunt his nightmares forever. But if he fails, Venus will die as surely as the atom-blasted Earth died; and Mankind will die also.
THE JUNGLE
Brainard's torpedoboat was in the wrong place at the wrong time when a salvo of shells flung him and his crew ashore in their wrecked vessel. Without a radio, they're as good as dead - unless they can cross the island through a jungle where every animal is a danger and the plants are even worse.
Brainard and his fellow Free Companions are hard men who've faced death in battle, but now their enemy is a green Hell that wants not only to defeat but to devour them ...
as it will some day devour all of Mankind - unless Brainard and his crew survive, and they can turn the lessons they've learned in the jungle against the even greater enemy that lurks in the Keeps themselves!
Hard-edged politics and combat written by a man who's seen both personally, displayed in a lush setting created by two of the finest SF writers of all time!
For the second novel the science assumptions are a bit dated or simply wrong.
First, the atomic war that destroyed all life on the Earth was a runaway fusion reaction that fused all the hydrogen in the Earth's oceans that turned it into a temporary star for the next one thousand years. I'm sure even Malenfant would agree that this could not happen
Second, the Naval Warfare is modeled after pre-World War I ship actions, it is assumed that all airplanes are automatically shot down by cannons that hurl their projectiles at a significant fraction of the speed of light, through an atmosphere no less! Also atomic power is banned because of the atomic war that that turned the Earth into a minature star, this of course begs the question, how could any sort of cannon hurl a projectile through an atmosphere at a significant fraction of the speed of light
without atomic power? In the category of atomic power, I would include fission, fusion, and matter/antimatter reactions, as they are all different types of atomic power. This is Pulp Science. By contrast
The Sky People is a Pulp Setting, but a hard science fiction book. It is possible for an advanced civilization to terraform a planet, this doesn't violate what we know as the laws of physics. I'd say anybody who could fire a projectile out of a cannon at 1% of the speed of light through an atmosphere, but without using atomic power is using a science I don't know about, and probably doesn't need atomic power anyway if he could accomplish that, also if the shell hit the ocean, or just traveled through the air, it would probably trigger fusion reactions in its wake simply by compressing the air in its path, that is assuming that it didn't vaporize and and explode itself and the cannon before it even left the barrel.
I like
The Sky People because it doesn't give me any of that stuff, the only assumptions I have to make to suspend my disbelieve is that Venus and Mars are different, because somebody fiddled with them in the distant past, their motivations are hard to phantom, but this is certainly physically possible, and you have millions of years to accomplish the terraformation of Earth and Mars, much better to believe that believing that Mars could be terraformed in a couple of centuries as Kim Stanley Robinson's
Red Mars/Green Mars/Blue Mars series does. Terraforming a planet takes a long time, and I'd rather have it over and done with before the story begins and have some mystery to solve rather than a multigenerational epic that is all about the process of terraforming than about the result itself. When Mars is terraformed in K.S.R.'s book, the story is just about over.