I recently finished rereading Heinlein’s 1956 novel. It’s still one of my favorites.
There are three main threads to the tale. The first is character driven: the narrator, who we first meet as a vain, arrogant, cowardly, xenophobic and not very successful actor, is enlisted to impersonate another man, a brave statesman revered by his followers who has been fighting for political rights for people who have been disenfranchised. Over the course of the story the protagonist begins to behave more and more like the man he is imitating, and the counterfeit virtue becomes increasingly real. The voice is the most individual of Heinlein’s narrators, who otherwise have a tendency to sound too much alike. This thread of the story does not require a SF setting, and strongly resembles the theme of the film and novel General della Rovere, released a few years later and set in Italy during WW II.
The second thread poses the question: to whom do ethical basics apply? Are the only true for Homo Sapiens, or do they apply more broadly?
The third is the setting, an attempt to create a plausible, possible and consistent portrayal of life in our solar system in the author's future.
This has now become an alternate universe story, for two reasons.
The first is that a lot of what we thought was possible in 1956 wasn't. We didn't know how thin the Martian atmosphere was, or how hellish Venus was beneath the clouds, or how efficient a nuclear thermal rocket could built given late 20th-early 21st century materials technology (it turns out that the massive engine, shielding and tanks for the bulky hydrogen propellant eat up a lot of the performance benefit of the higher exhaust velocity). Another half century of particle physics have given a lot of evidence that a Heinleinian torchship that simply stuffs mass into the converter and turns it all into energy is probably not practical in the universe we live in.
The second is that even based on what was known at the time, Heinlein was wildly overoptimistic about the prospects for human colonization of the solar system. Observations from earthbound spectroscopes had already indicated that neither Mars nor Venus had the relatively hospitable levels of atmospheric oxygen and water that Heinlein assumed in his stories.
Even with the full weight of Heinlein's thumb on the scales of extrapolation, the economics of colonization and space travel in his future history didn't make much sense. One of his stories, Space Jockey, assumed cargo could profitably be shipped from Earth to the Moon for about $300 a pound in 2010 dollars. This is at least two orders of magnitude better than we can do today. Even so, it's hard to find physical products that can be traded between planets with these sort of transport costs. Even the optimistic Heinleinian Mars could be described as a colder Gobi Desert with less air, so it's hard to make a credible economic case for planting a colony there.
In hindsight, the story was not very successful in extrapolating the impact of television, a technology already in use, on political campaigns or the profession of acting. In spite of references to "stereo" the political campaign and the acting career of "The Great Lorenzo" seem firmly rooted in 1956 or earlier.