Implausible and impossible to put down- like all of Heinlein's books I've read its hero is a man of action and boundless self-confidence, a wisecracking all-American cowboy figure who brushes obstacles aside, a genial dictator figure who knows that as long as he's left in charge everything will be o.k. The voice is always the same - and I can see why the new wake of science fiction writers reacted against Heinlein: Aldiss, Moorcock, Ballard, Dick. Heinlein's Pax Americana and paternalism vision of the future certainly does have fascist overtones. But he's still a great storyteller, his books filled with mind-bending concepts presumably achieved without the help of the consciousness expanding substances that inspired some of his successors.
Yes, the Bonforte character was a very macho autocrat...Who cares? Nevertheless, “The Great Lorenzo” doesn't quite conform to the macho 'tit man' narrator as Heinlein... although the authorial voice does creep through in interesting ways in his stereotyped descriptions of Lorenzo's camp-actor personality and co...Heinlein enjoyed challenging established ways of thinking, and for most of his great period of writing liberal politics was on the rise, so he took great pleasure in poking holes in political sacred figures. The conservative viewpoint is already being expressed quite vocally in SF - take a look at Baen Books for a few examples. Some might argue its a viewpoint that doesn't merit expression, but I'm not sure what it says about contemporary literature if it can't manage a political dialogue.
My grumble with it is that I didn't really think it was proper SF - which may sound odd given the presence of Martians etc., but what I mean is that at its heart, the plot is about a man masquerading as someone else, and a pretty much identical story could be told in a real world setting. What I enjoy in SF is the way it changes the rules of the world and explores the consequences of these changes. I recently read Richard Morgan's brilliant “Altered Carbon”, which was superb in the way it used its central "rule change" (that people's personalities get stored in a chip implanted into the cortex, which can then be transferred into other bodies) to drive the plot and then use that plot to show the effects of this technology on people and society.
As I say, not that rewarding as SF, but fun and certainly intriguing.
SF = Speculative Fiction.