Alas, Babylon by Pat Frank
This book was originally published in 1959 but is remarkably relevant today. I think I was supposed to read it in high school but didn't remember much of the storyline. I was surprised to find out that it is set in central Florida, not far from where we used to live. Several nuclear explosions cause massive casualties and total power outages. The small fictional community of Fort Repose pools resources to survive. It had a hopeful ending which I appreciated.
One Second After by William R. Forstchen
Published in 2009, this book has a similar theme but a more modern day setting. It starts out pretty slow and it took me four tries reading chapter one before I got to chapter two. This book is set in a small town near Asheville, North Carolina after some sort of EMP event that causes power outages and general chaos. The book is divided into chapters based on how many hours, days, weeks after the event. The story follows the family of a former military man currently teaching history at the local college. He manages to unite the small community and pool skills and resources for their survival.
The Rule of 3 by Eric Walters
This book is a newer book published last year and written by a man who was born around the time Alas Babylon was written. I think it is technically a young adult fiction - the main character is a 16 year old boy. The story is set in an unnamed midwest city (it references Chicago and Detroit) following what appears to be an widespread EMP. The mastermind behind their survival is a neighbor who is retired from the CIA. The title comes from the fact that you can survive three minutes without air, three days without water and three weeks without food. I'm currently reading the sequel called Fight for Power.
Of course they were all fiction, but the main theme with all three books is that in order to survive a widespread disaster, small communities are going to have come together and cooperate. A community needs to establish their own sort of law that is based on justice and fairness. Disobedience is handled swiftly and harshly in order to discourage further lawlessness. They need to pool their resources like food and fuel, talents of leadership and common sense and skills like medical and military training.