Off Armageddon Reef by David Weber is an expansion, and a significant change, of a story from his moon series. It reminds me of Heirs of Empire.

Heirs of Empire story, at least the half related to this: Five folks end up on a planet where there is military hardware in the sky and the people of the planet have been taught that space farers are demons. The planet’s inhabitants have spent thousands of years with water and wind technology only, though they have re-developed semaphores, muskets, and cannon. Only those developments which pass the Church’s requirements are allowed to be put into production. The five have to bring knowledge of space to a people whose religion, made up by their ancestors as a reaction to a plague that spanned the universe, requires their death. They start a religious war, all unplanned, and explain the facts to a planetful of people. After that, they send a message home to their families who are under the impression that they, like the other thousands on their ship, are dead.

Off Armageddon Reef story: Aliens, not a plague, destroy most of the human universe. The leaders of Operation Ark declare themselves Archangels (ark angels, get it?) and start a new religion. They leave military hardware in the sky to destroy something– probably any techology past a certain and unknown point. They don’t just lie to the people they’ve brought to the planet, they give them false memories. They murder those who use electricity. And so for 900 years the planet has been using wind and water technology, because nothing else has been able to be developed under the Church’s proscriptions.

The main character is not five kids, but a dead woman who uses her brain patterns in an AI, kind of, to create someone who can help the planet, a guy named Merlin. He goes to the one group on the planet who don’t have serfs or slaves and keeps their heir from being assassinated. And, as above, a religious war starts.

Heirs of Empire was short, had two stories in the novel, and resolved the whole situation in one book. Off Armageddon Reef is a single plotline, twice as long-at least- as Heirs of Empire, and just begins the religious war.

Heirs of Empire has two romances in it. Off Armageddon Reef has none.

Heirs of Empire’s folks thought the kids were dead. The hero in Off Armageddon Reef is dead. Furthermore she’s been dead for 900 years.

Heirs of Empire brought an entire planetful of people back into the human empire. Off Armageddon Reef’s planet is the last of the human empire and might have to fight off the aliens who’ve been pillaging the universe for 10,000+ years if they actually do get technology back.

Heirs of Empire can use the prince’s ability to turn off the military hardware in the sky. Off Armageddon Reef’s military hardware was made to NOT be shut down by anyone.

We’ll see how much the plot diverges as the series goes on… But it’s sad that the main character of Off Armageddon Reef is dead.