Common themes keep cropping up in Philip E. High novels. Not every story includes all, but all include some of:
There's obviously a lot of wish-fulfillment going on here, with the initially wimpish protagonist eventually turning out to be the saviour of the human race, and with all interpersonal relationships made perfect, and effortless, by some external "change". But despite the naivete (or maybe because of it?), there is something rather fun about these books. I think it might have something to do with the fact that the story isn't about an individual's fight; it is usually a group, working together, who manage to prevail.
Richard Denning discovers that he is a specially bred covert agent from a parallel Earth that has been taken over by aliens. These aliens have stopped that Earth's rotation, dividing the humans into Co-Temps, "Buns", and "Lollies". His Lolly controllers want to oust the Co-Temps. But Denning, and his genetically engineered twin Liston, have other ideas -- they want to defeat the aliens completely.
Maynard is an ordinary man doing an ordinary job, until one day he is abducted by a criminal gang. He escapes, but is then abducted by another group, who say they are the good guys. He learns there is a silent war being waged between the good guys and organised crime, a war that most of the populace know nothing of, but in which he has become involved. His accurate dreams of criminal activities and alien presences worry his captors, as does his sudden ability to recognise the Enemy. But this is all part of a larger evolutionary change affecting humanity, like caterpillars becoming butterflies, and the Enemy decide to go off to their own planets, and happily devolve. And all these changes come in useful when the aliens invade...
All of the usual High tropes, but rather more rushed and compacted than usual in this slim volume of barely 100 pages.
Earth has been invaded by the alien Confederation. But they're not here to conquer, they're here to hunt. And the Hunt Master's race may have a very important reason for arranging things this way.
This has many of the elements of a Philip E. High novel: the protagonist is a member of a group of humans made immortal by being exposed to Intrusium; he does not remember this initially, having had to force himself to forget, to protect himself from the alien Yend; the members of the group have their personalities "cleansed" by a friendly alien.
There's even early nanotechnology here, with a supercomputer being able to construct copies of anything from an "atomic map". But the whole story is put together very poorly. The first half is choppy and fragmented, being taken up by hopping from one weird parallel universe to another to escape the Yend, with very little plot development. Then the fight back is much too easy, especially given the odds of a million to one against! A big disappointment.
The alien Asdrake race conquer planets by seeding them with micro-organisms that kill off the intelligent life. But when they try this on Earth it doesn't work -- instead it gives all adult humans parapsychic powers. This sends many mad -- but some manage to control and investigate their powers. It turns out that humans have always had these powers, but millions of years ago a powerful race in the galaxy blocked them. The race is on to find out who, and why.
This is an absolutely typical High novel: the hero is just an ordinary man, but bands together with other like-minded people; the newly discovered powers include the ability to become one with one's complementary other; the humans manage to outsmart the rest of the intelligent creatures in the universe. The science is risible in places: there's talk of the aliens noticing billions of years ago that the humans' powers would need to be blocked, and weapons designed to destroy the Earth, when turned on their attackers, suddenly become capable of destroying galaxies -- but there's also some good stuff, about what you have to do if suddenly you discover that all your wishes come true.