So, most of the population of USA is wiped when an engineered superflu escapes a military laboratory. After the initial chaos the survivors coalesce around Mother Abagail, an ancient pious prophet-like figure, and the "Dark Man" her antithesis. After settling in Boulder, Colorado, the good guys (aka Free Zoners) suffer the birth pains of building a new society with much navel gazing about republics and not repeating the "mistakes" of the past -- a recurring theme -- while the Dark Man, like any good fascist dictator, gets the trains running on time and crucifies anyone who disappoints or disobeys him. The Dark Man is hell bent on wiping out the good guys. The Boulder society sends spies into the Western states controlled by the Dark Man who via magic knows all their movements except those one spy who happens to be mildly retarded man. The final showdown comes when Mother Abagail's dying advice is to send 4 sacrificial lambs to the Dark Man's capital in Las Vegas.

I read the expanded edition published in 1990 which clocks in at 1000+ pages. Its an easy read -- a native English speaker is not going to be reaching for a dictionary or re-reading passages to understand some point -- but its lengthy and I found myself skimming chunks of text towards the end.

Initially the tale offered what I felt like a new twist on the end of civilisation story -- population wiped out but infrastructure and any number of resources and artefacts intact. There was no all destructive war for example so things, including weapons of mass destruction, are just lying around waiting to be found and used -- a point made explicitly in the book. This does away with some of the standard problems, like getting around, but introduced new ones and the possibility of rapid changes in the balance of power.

But the Dark Man can just use his remote sensing ability to keep tabs on the Free Zoners, make animals obey him, drive men mad with his stare so I'm not sure why he needs any of the military hardware or the people gathered around him. Mother Abagail for her part communes with God while any number of characters have premonitions in the form of dreams.

Ultimately, I wouldn't recommend it unless you're wanting to kill (a lot of) time with a mildly entertaining tale without any challenge to your brain.