This series began very weakly with "Dies the Fire" and particularly the 2nd in the series, "The Protector's War". It took off significantly with the third one, "A Meeting at Corvallis". Now we bounce ahead another 12 years, almost passing the generation that grew up and faced the Change and now starting to open up a world increasingly lived and run by people who grew up after the Change.
As such, there's a constant divide that exists between the older characters and the younger; its remarked upon directly a few times, almost a sort of "old world blues", where the people who knew the modern world of computers and electronics are still existing in this post-apocalyptic pre-industrial world and still feeling a bit as though they were not wholly 'there', not truly belonging to the new world.
The sense that the needs of survival, not just physical but mental and emotional, meant that they had to essentially roleplay as a new version of themselves. There's still a sense of play about the whole lording around, calling people "Barons" or "Lords", wearing metal armor and using long spears and swords. There's a sense that if the Change were suddenly undone, they would be shocked, possibly suffer a lot of PTSD, but would ultimately be relieved and return to their old way of lives.
The so-called "Changelings", kids who grew up after the Change, are absolutely in their element. This is the real world for them. If the Change were undone, they would be the strangers in a strange land, forced to adapt to a world of utter fantasy to them.
As Ken Larson said in an earlier book, him and his daughter's and Mike Havel's generation is essentially going to be the last to know the stuff of easy access to resources, air conditioning, cars, instant electronic entertainment, and more than that, a level of freedom from base survivalism, one where leisure and thinking beyond the thoughts of crops and livestock and life or death politics. Their generation will become the stuff of legends, like Heracles, Romulus, Gilgamesh, Huangdi.
As well, we now start to see a very, very subtle, growing sense of the mystical starting to emerge from this world. And because of how the Change worked, changing the laws of physics, it's entirely possible that this sudden seepage of supernatural elements is something directly related to the Change, and warranting further contemplation, particularly for the older folk before they begin to grow old and die.
A newcomer enters the series, Ingolf Vogeler, a rancher turned mercenary from Wisconsin who was tasked to investigate the unusual occurrences in Nantucket in the far east, where the events of the "Island in the Sea of Time" series began, starting off the Change and this series.
All grown up now as well are the likes of Rudi Mackenzie, son of Juniper Mackenzie, Mathilda Arminger, daughter of Norman Arminger, Odard Liu, son of Eddie Liu, and Ritva and Mary Havel, daughters of Signe and Mike, Lord Bear. A supernatural incident experienced by Vogeler (including a possible teasing of alternate universes or timelines) leads him west to Rudi and his gang, and to the grand quest to Nantucket to get ahold of this "Sword of the Lady" or whatever it is.
That means this group, including a Benedictine warrior-monk, has to travel across the entire continental US. The journey massively opens up the world of the Change, as we get to see colorful additions such as the United States of Boise, clinging to the dream of old America while taking on vaguely Roman style military composition, or the Mormon Republic of New Deseret, in a dangerous position as buffer state between the western factions and the vast, Montana-based cult, the Church Universal and Triumphant (an actual real life cult) which has taken on a "Fallout New Vegas Caesar's Legion" style, swarming the lands, massacring men, enslaving women, and conscripting children to be indoctrinated and trained to be warriors of their faith.
The CUT, led by their Prophet, initially come across as something of an almost one-dimensional cartoonish evil faction, with hints of supernatural abilities among themselves as well, and a seemingly unrealistic sense of invincibility in their nonstop conquests.
But later on in the book we get to see the Cutters, as they're called, at the ground level; from the point of view of the conquered, forced to adopt the religion and take part in the atrocities. It's a typical but necessary and realistic narrative device to depict large swaths of the "ravenous horde" enemy as actual normal humans, some of them being forced by circumstance and others simply thriving in a new life where their old ones promised them only a hard life on a small farm or ranch.
The greater realm of politics unfolding in this new world is immensely entertaining and if you've already read the Nantucket series beginning with "Island in the Sea of Time", then Rudi's quest also takes upon a much larger significance and level of interest.