It's Year 24 of the change, when humanity was deprived of the use of engines, electrical equipment, guns and explosives. The early books in the series show us how societies rebuilt after the chaos and mass die-offs that ensued. The Sword of the Lady takes us on a quest across a changed north america to retrieve The Sword of the Lady. Our heroes are all young leaders-to-be from the various small states that have developed over time. From the start of the series we've had hints that there may be other forces at work, be they gods, post-humans, Alien Space Bats, or whatever. This becomes clearer, although we mostly see them reflected through the varied spiritual perspectives of the characters which just adds to the richness of the tales.
So far, so Lord of the Rings, you may be thinking, and there's enough nods to this, and many other works, to keep you grasping at recognition, or sometimes laughing out loud at a subtle reference to something you know well. But this is it's own story, a muscular adventure, with great attention to detail, whether to dialect, the smell on you after many many days on horseback or fighting with bow and sword, or the impact of good food after such a journey. And the fighting, well he can write a hell of a good fight scene, and there's plenty of those, each different enough so it's not repetitive. We've also got characters we can care about, good and evil manifesting in powerful ways, a quest that makes sense, multiple levels of understanding and just very, very good writing. Make sure you've got some days off work to get it read... you won't want interruptions.
Having re-read the whole series many times I'd no problems with putting it all in context, so it's hard for me to know if a new reader would find this book able to stand by itself. I suspect it will, there's some background provided but no great info-dumps to spoil the flow, and as I say it's a damn good story.