The Castle Keeps falls squarely under 'starts bad then gets worse'. The agent of collapse in this work is population and also environmental damage done by an uncaring public. Early on in the book the cops give up even attempting law enforcement and go on killing rampages that outstrip the criminals in violence. The citizens of major cites ignore violence inflicted on their fellow man (Offutt uses a case in New York where a woman is raped in front of many witnesses and no one helps as 'proof' people will care less about their fellow man as time passes). He also uses the use of DDT to extrapolate how man will continue to destroy his environment. I think he is right we will eventually do this to our selves but not however in the short time span he predicts. Still this is good read. The deceptions of chaos in the city are great as are the two battle scenes. But if you are like me and are a PA purist I recommend that you should skip this one.
Two other books go hand in hand with this book. The first is The Last Gasp by Trevor Hoyle. He stays with the 'man is turning the planet into a cesspit' theme to its logical conclusion. This was a book that took me quite awhile to read. It just struck me as sorta boring. It was however apocalyptic, just not much of a page turner.
The other companion book to The Castle Keeps is Make Room, Make Room. I admit that I haven't read this one yet. I do own it and I intend to read it one day. I know that it is not apocalyptic though. Life is hard because of over population. I mention it here because of what I just mentioned and also because it got a short mention in The Castle Keeps. I own and have watched the movie Soylent Green and perhaps one day will post a compare/contrast dealing with them both.