Rule of Three

Rule of Three starts with a student working on his paper at the last minute. Then all power shuts down and things go haywire. The problem appears to be more widespread than just power - all computers (or anything containing them) are shut down. An explanation is never given for why. However, the power outage is widespread. Luckily, the protagonist drives an old car, so he is still able to get home. (He is also able to drive his "crush" home to her farmhouse.) Once home, he meets up with his neighbor, a former government operative who is also a survivalist.
The boy's mom happens to be a police officer and initially works to keep things in order. They arrange for people to "buy" goods on credit from local stores (thereby forstalling the looting attempts.) However, things quickly go downhill as the outage goes on. Eventually, they focus on their neighborhood. They set up security checkpoints, build a wall and recruit the local farmer (who happens to be the father of the girl that the boy likes) to come in and help farm plots. They seem to have a viable community.
The boy eventually gets his ultralight airplane to run and explores other areas. They discover the police station has been destroyed by a rocket launcher, probably by a group that has a Cessna. They also open up a mutually beneficial alliance with another community. Later, the Cessna group destroys the other community and murders anyone they can find. From there to book works towards its violent climax, complete with airplane fights and boy falling in love with girl.
It feels very similar to other "collapse of modern culture" novels, though this is told from a high school perspective.