The Last Centurion - John Ringo
Finished this recently...in like 4 days which might be a personal record
Great read, I highly recommend it.
It's been discussed here probably a dozen times or more.
I found the fuel and ammunition logistics of the first half of the book stretching credibility.
The last half of the book had potential for providing a fast paced look at restoring order to and eventually rebuilding a collapsed America ended up being mostly a boring-as-fuck discussion of EVERY aspect of modern farming.