The novel deals with an unexpected electromagnetic pulse attack on the United States as it affects the people living in and around the small American town of Black Mountain, North Carolina.

A retired U.S. Army colonel and Gulf War veteran, he had moved to Black Mountain with his family when his late wife Mary, a native of the town, was dying from cancer.

At 4:50 p.m. (16:50) Eastern Daylight Time on the second Tuesday of May, the first day described in the book's narration, the phone lines in the town suddenly go dead, along with all the electrical appliances.

Every modern electrical device is disabled, destroyed by what Matherson is beginning to suspect was an electromagnetic pulse (EMP) attack on the United States.

Residents of the nursing home in town, where Matherson's elderly cancer-stricken father-in-law is being cared for, are at risk.

It takes two months before a working antique telephone can connect Black Mountain with the nearby town of Swannanoa.

Matherson's daughter, Jennifer, eventually dies due to a lack of insulin and is buried near the family home.

It is learned that the EMP was generated by three nuclear missiles launched from offshore container ships.

The U.S. government believed that an alliance between Iran and North Korea conducted the attacks, and retaliated by striking both countries with nuclear weapons.

The U.S. withdrew all of its overseas military forces to aid in rebuilding and humanitarian work at home.

The book also explores the increasingly intimate relationship Matherson develops with Makala Turner, a single, childless nurse among those stranded by the pulse.

The book contains a brief non-fiction afterword by U.S. Navy Captain William Sanders, regarding EMPs, which includes references to the reports of the United States EMP Commission[3] and the book The Effects of Nuclear Weapons by Samuel Glasstone and Philip J. Dolan, published by the United States Department of Defense,[4] which is a technical description based on early nuclear tests.

[6] In November 2021 the TV rights for the book series were licensed MPI Original Films.

Now, One Year After returns to the small town of Black Mountain, and the man who struggled so hard to rebuild it in the wake of devastation-John Matherson.