Atlas Shrugged, for those of you who never read it, can be summarized entirely fairly as follows. Unknown to our viewpoint characters at first, an inventor named John Galt has invented a "free energy" machine, a motor that runs on ambient static electricity and the Earth's own inertia and puts out enough electricity in a fairly small unit to power almost anything, including vehicles, force field generators, energy weapons, even an invisibility cloak if you use a big enough unit. He invented this while working at a company where his contract gave them rights to stuff he invented on the clock, like most professional engineers and inventors, but he assumed that as the inventor, he was entitled to all of the profits from this fabulous new invention. The company's management and other employees, though, saw just how much resentment would happen if one company owned the monopoly on an invention this valuable, and started making plans for how to invest some of the profits into charitable ventures, so they wouldn't get the whole thing taken away from them via eminent domain. John Galt, outraged that anybody would even suggest that he or the company he worked for owed anything to the nation that provided his education, protected him from infectious disease outbreaks, protected him from Communist invasion, built the roads that got him to work each day, provided the police that kept him safe, and provided the court system that protected his property rights at all, sabotaged the Galt Engine, so nobody could have it.
Then he went further and, in a fit of offended pique, promised to "stop the motor of the world," to kill 90% or so of Earth's population by intentionally wrecking the economy. Which he then did. How? By finding every other competent engineer or manager in the US and persuading them to be just as selfish as him, just as unwilling to pay back or protect their country; he declared a covert "strike of the mind," as he called it. He hid them all in a secretive compound in the Rocky Mountains, protected by force field and invisibility cloak, and waited for the US economy to collapse, which, obligingly, it did -- because John Galt had carefully sabotaged the bridges and railroads that made it possible for fuel and seeds to make it from the coastal cities to inland farms, and make it possible for food grown on inland farms to make it to the coastal cities. And as chaos was breaking out, he and his fellow inventors hijacked every radio transmitter in the US to broadcast his manifesto: You all deserve to die, for asking us to pay you back even one nickel, because we are all so selfish we don't consider any of the things you all paid for out of your taxes and that you did with your labor to have been at all helpful to us as entirely self-sufficient brilliant inventors and managers. So die.
And that's where the series is interrupted. But from where the third book picks up, and by applying a little common sense, we can outline the main plot points, if not the characterizations, from the untitled middle volume, the one I'm whimsically calling Atlas Shrugged 2: Shrug Harder. When the previous book ran out, America was winding down to what was clearly going to be the last harvest, ever, and the Strikers were planning for the day that they, as the only people possessing any high tech or any capability of mass production of food or anything else, would ride out of their hidden Colorado fortress as humanity's saviors. They were pledging to themselves to build a new world based, as John Galt's manifesto had promised all Americans, on the virtue of selfishness. They assumed that a grateful (or at least desperately needy) and vastly reduced in number population would welcome them as liberators, chastened and having learned their lesson. Except that we know from the third book that that's not what happened, and anybody who knows human nature should have been able to predict that.
Outside the valley, the conversion to local subsistence farming and the work of scavenging the dead cities for any usable metal would have been rough. No time or energy would have been available to save even minimal technology. We're looking at a collapse all the way back to (at best) early iron age levels, maybe even all the way back to the bronze age, and nobody will even have time to teach the next generation to read and write. But one thing very clearly did happen, in every survivor's village, and became world-wide policy as soon as even minimal travel and communication made it possible for the chiefs of the scattered villages of survivors began to reunite society into any kind of a civilization, and that is a fierce determination to make sure that the next generation remembered who had done this to them, and why they had done it. They would have educated their children to remember the names and descriptions of every one of the hated Strikers who had personally murdered four and a half billion people for a political point. And they would have educated their children that one idea, one idea in the Strikers' twisted minds, had lead to those four and a half billion deaths, the greatest act of genocide in human history: selfishness. How far did they go to eradicate selfishness? They went so far as to eradicate the first person pronoun from the language.
Because she died without telling anyone, it's not entirely clear how Shrug Harder would have ended. We know that at some point, at least one of the Strikers does leave Galt Valley. He built a high-tech home, stuffed it with a library and all the wonders of the Strikers' science, and then (apparently) set out to make contact with the nearest survivors' village, assuming that they'd worship him as a god for his technological superiority, assuming they'd cheerfully feed him and provide him with anything he wanted for the products of his labor. And, rather obviously, they did what anybody would do: they executed him for crimes against humanity. His technological redoubt was never found. Did other Strikers meet the same fate, or are they all holed up in Galt Valley still? We'll never know. But that brings us to the book that would clearly have been relabeled once the trilogy was complete ... Atlas Shrugged 3: Anthem.
Anthem is actually the best book of the three. And it's a credit to Rand that she realized just how monstrous the real results of the Strike would be. Many, many so-called Objectivists and Libertarians, who only read the first book, thought they were supposed to cheer for the Strikers, believed the Strikers' personal delusion that the Strike, and the resulting mass genocide, would usher in a techno-libertarian paradise on earth. No, in Anthem we get a view of John Galt's Earth from the viewpoint of someone who grew up in the next generation, never having known a technological world, knowing only a world in which selfishness is labeled the ultimate sin. The massive die-off from John Galt's strike has resulted in the rise of the most vicious and backwards and cruelly unfair totalitarian regime in human history. And our nameless hero slowly has it dawn on him that the ruling council is so afraid of selfishness that they're retarding any attempt to restore human technological civilization, no matter how miserable and stunted low-tech life is, until they figure out some way to integrate technological progress into their civilization without anybody being able to claim credit for it. Which cannot possibly work.
Our nameless hero, having found working light bulbs and a working electrical system in the ruins of the city his farming town is built over, even offers to forgo personal credit for the discovery, offers to accept no credit for it at all. But their paranoia and terror that he's a prospective future Striker pushes them to hound him to the point where in desperation he and his girlfriend flee the city into the uninhabited wasteland ... where they find the technological trove, and the library, left behind by the unnamed Striker at the end of Shrug Harder. He and his now wife settle down to raise children, to use the subsistence farming skills they learned from their own civilization to sustain them, to gather any other stragglers who escape the cities, and to stay out of sight until they find a way to overthrow the horribly dictatorial Councils that rule the world and lead it to a saner middle ground, one that (presumably) knows to watch out for civilization-wreckers like John Galt but that also knows that giving personal credit is a prerequisite for technological advance. It is, if not an entirely happy ending, a hopeful one.
Oh, except for one thing. I made up the whole bit about the second book. I don't think Ayn Rand was aware enough of the limitations of her philosophy for her to realize that the communo-primitivist dictatorship of Anthem, not a techno-libertarian utopia, would be the inevitable outcome of a genocide of almost the entire human race by techno-libertarians. Oops. Never mind, then. Sorry!