One Second After is a realistic "what if" - one way of imagining the consequences of a weapon called an "electromagnetic pulse," in which, in a moment, essentially all technology is friend. No more working cars - if they had any electrical components. No more running water and no more communication beyond messages run by hand.
For John Matherson, this terrifying possibility becomes a reality when his small North Carolina town is suddenly cut off from the world and dropped back into the dark ages, with no clue as to the state of the world. With no refrigeration, only the food they have on hand to feed the entire population and nerves on the edge of collapse, all John really knows is that unless a few of them band together to start making some tough decisions, chaos will be the ruin of them all.
Yes, it scared the pants off of me. His scenario is plausible and well thought enough that the narrative is believable and keeps you interested (you'll be wanting to go out and stock your basement with food and pioneer-living equipment). Yes, I had tears well up a couple times and I appreciated that he kept his plot realistic enough that I wasn't needing to suspend my disbelief that often. There is a nice balance between his experiences at home and in the community and I think what I liked most about the way the story is told is that there is only one point of view. We only know what John sees and hears - there aren't any flashes to news stories or other parts of the world, we are just as in the dark as John is and that made the story that much scarier.
The language is a bit rough at times and there is some gore, for sure - when all the rule books are burned, the cuckoos come out to play and this book is no exception. My only gripes were dialogue that sometimes fell into obvious statements and some of the chronology at the end of the story felt poorly done, but he smoothed it out and even the ending felt just ambiguous enough. If you don't like disaster and survival stories, this won't get five stars from you, but as a reader that loves this stuff, it was an interesting twist.