I'm sure its been mentioned in this thread- Lucifer's Hammer by Larry Niven & Jerry Pournelle. Awesome book, very long, very detailed and a great read.

I'm a big fan of Clancy so I think I know what your looking for. This is the closest in my experience.

Just got done reading this and it was great. Also got done with the Postman, which was pretty good as well.

I'm currently re-reading Edgar Pangborn's post apocalyptic novel "Davy".

I would recommend it highly to anyone who likes a touch of Twain in their reading. Pangborn also wrote "Company of Glory" set in the same milieu.