Dies the Fire — S.M. Stirling

The Change occurred when an electrical storm centered over the island of Nantucket produced a blinding white flash that rendered all electronic devices and firearms inoperable--and plunged the world into a dark age humanity was unprepared to face....

Michael Havel was flying over Idaho en route to the holiday home of his passengers when the plane's engines inexplicably died, forcing a less than perfect landing in the wilderness. And as Michael leads his charges to safety, he begins to realize that the engine failure was not an isolated incident....

Juniper Mackenzie was singing and playing guitar in a pub when her small Oregon town was thrust into darkness. Cars refused to start. Phones were silent. And when an airliner crashed, no sirens sounded, and no fire trucks arrived. Now, taking refuge in her family's cabin with her daughter and a growing circle of friends, Juniper is determined to create a farming community to benefit the survivors of this crisis....

But even as people band together to help one another, others are building armies for conquest....