Henry Kuttner: The Creature from Beyond Infinity

Henry Kuttner's novel The Creature from Beyond Infinity was originally serialised in 1940 - as A Million Years to Conquer, which is a much better and more accurate title - thus making it eligible for the 1941
Retro Hugos. Which is why I read it. It was published as The Creature etc. in 1968, which means I probably first read it back then - indeed, some aspects seemed vaguely familiar to me.

So... The story concerns Ardath, the last member of a dying race from a doomed planet, his ship downed on earth millions of years in our past, his mission to wait In stasis until intelligent life develops, then select the brightest of the race in various time periods, hopping in and out of stasis with his specimens, and then breed them into a super race, and recreate the splendour of his own long-lost civilisation on Earth.

The plan goes terribly wrong when one of his first specimens turns out to be a power-mad and brutal, but crafty, barbarian who acquires Ardath's scientific knowledge and conceals the fact from his 'benefactor,' waiting for the chance to seize control of Ardath's orbiting space ark and use its advanced capabilities to conquer the planet.

That time comes in the mid-20th century, when a super genius named Steven Court, studying anomalies of all kinds to try and solve the mystery of a mysterious plague before it becomes widespread, locates Ardath's ship in orbit and builds his own to go see who's been observing humanity.

It's a very 40s kind of story, fast-paced and full of manly men and beautiful 'girls,' with atomic power being the cure for everything, and an unquestioning belief that eugenics and super-intelligence will bring us a bright new world - though Kuttner, perhaps due to his close working relationship with C. L. Moore, acknowledges that women can be super geniuses too, and that coldly intelligent men need to waken their emotional sides to be truly great.