Sunrise by Mike Mullin

The Yellowstone supervolcano nearly wiped out the human race. Now, almost a year after the eruption, the survivors seem determined to finish the job. Communities wage war on each other, gangs of cannibals roam the countryside, and what little government survived the eruption has collapsed completely. The ham radio has gone silent. Sickness, cold, and starvation are the survivors' constant companions.

When it becomes apparent that their home is no longer safe and adults are not facing the stark realities, Alex and Darla must create a community that can survive the ongoing disaster, an almost impossible task requiring even more guts and more smarts than ever -- and unthinkable sacrifice. If they fail . . . they, their loved ones, and the few remaining survivors will perish.

This epic finale has the heart of Ashfall, the action of Ashen Winter, and a depth all its own, examining questions of responsibility and bravery, civilization and society, illuminated by the story of an unshakable love that transcends a post-apocalyptic world and even life itself.

This book is part of the "Ashfall" series.
Here are some other books from this series: