Marked by Fortune - Ann Gimpel - Bog

Magic levies a steep price on anyone brave enough or stupid enough to dabble in it.
Wizards never forgave Ned for not being one of them. They didn't exactly come out and say his life was expendable, but they didn't have to. He figured it out fast enough when they conscripted him into their long-running war the second he was old enough to fight. Isolated, different, he puzzled out how his brand of magic worked on his own.
Fleeing the tide of doom wiping out humanity, Amanda and her family escape to a remote corner of California, where they eke out a hardscrabble existence. With her parents at each other's throats and her brother mysteriously gone, Amanda encounters malevolent power beyond her wildest imaginings. Captured by the Undead, she's about to join their ranks when Ned shows up.
Defying a direct order from his wizard battle lord, Ned dives into the fray. He might not know Amanda, but it doesn't matter. She's in trouble and needs his magic.
It's good enough for him.