Earth and Firma were mirror worlds. Because they were on a single time-track, Earth was destined to repeat the dangerous history of Firma--which had been stopped in its rotation around the sun by Aliens.
Denning and Liston were twin humans, biogenetic supermen with a single mission: to get Firma moving on its axis again and destroy its Alien conquerors. Though Firma was Liston's universe, Denning had to aid him, or Earth, too, would one day be burned to a cinder by the heat of the sun.
There was one scene in the middle where I got a little tired of the ongoing action which is the reason for the minus. Otherwise, it is a stunningly good 15x page novel with interesting characters, a good story, and just plain fun. Unlike most hard scifi, which is based on the extrapolation of one theory, this one includes several - alternate worlds, biogenetic breeding, alien invasion, and the effects of stopping and starting a planet's revolution. I recommend it if you can find a copy.
Alien insect invaders have halted the rotation of an alternate earth and for some unknown reason that is not fully expanded upon. Two genetically engineered "supermen" are meant to help the rather pathetic resistance fighters in ousting the aliens but they are operating to their own plans in the end and are betrayed by their creators.
Once read this when very young and thought I'd see how time had been to it, like myself it has not aged well. The story started off promising good stuff and sort of turned into a polite gentleman's sparring match, the only phrases missing were "spiffing show old chap." & "I say old man, jolly good show." Pipes and slippers, cardigans with the obligatory leather elbow patches and spitfire moustaches.
I rated this novel " C " when I read it June 10, 1974.
My rating system: Since Goodreads only allows 1 to 5 stars (no half-stars), you have no option but to be ruthless. I reserve one star for a book that is a BOMB - or poor (equivalent to a letter grade of F, E, or at most D). Progressing upwards, 2 stars is equivalent to C (C -, C or C+), 3 stars (equals B - or B), 4 stars (equals B+ or A -), and 5 stars (equals A or A+). As a result, I maximize my rating space for good books, and don't waste half or more of that rating space on books that are of marginal quality.
It's fine. This book is a prime example of bad writing. The author clearly came up with the end first and later forced all his characters to that conclusion without much plot depth or character development (a.k.a., no drama). It is sad to see such great ideals in a book fall flat because the author did not care about the journey to the destination, but rather the destination itself.
Favorite Quote: "Every day one meets the dreamers - the living dead who cannot distinguish between the dream and the reality." - Marko, Twin Planets