Ariel: A Book of the Change — Steven R. Boyett

Five years ago the lights went out, cars stopped in the streets, and magical creatures began roaming the towns and countrysides of Earth.

Pete Garey, a young loner who survived the Change and the madness that followed, spent two years wandering and scavenging the near-deserted cities and towns alone -- until the day he encountered an injured unicorn. He nursed her back to health and named her Ariel, and an unlikely friendship was formed.

But unicorns are rare even in a Changed world -- and the power of their magic is highly prized. A necromancer in New York City covets that power and will stop at nothing to possess Ariel, dead or alive.

Sought by bounty hunters both human and inhuman, Pete and Ariel decide to make a stand against their enemy -- and journey to confront the dark sorcerer in the ruined heart of the city he has made his own twisted kingdom.