The October Trilogy by Heather Killough-Walden

October has come, the leaves are changing, pumpkins are grinning, and an ancient god of death is awakening from an eternity of solitude. He scents a soul on the wind, as fresh and promising as the first day of fall, and as sacred. For the first time in his endless existence, the death god Samhain realizes that with the woman who possesses this soul, he does not have to be alone.
But he must act quickly. This is the sacred time of year when the doors between realms are open at last. It doesn’t last long, and Logan Wright’s spirit is calling to him.
Samhain leaves the world of the dead to enter that of the living, find the young woman who carries the mate to his soul, and make her his queen. He becomes “Sam,” the tall, dark, and eerily handsome stranger who suddenly has Logan’s school buzzing with secretly carnal desires, but whose piercing, all-knowing eyes are for Logan alone.
However, Logan is strong. Her hard-knock will, formed of misfortune and inherent goodness, is not only at the heart of what Sam desires in Logan, it is the very same thing that causes her to resist him. Sam isn’t prepared for Logan’s defiance, and when she runs from him, his menacing fury ignites a firestorm chain reaction of events that turn this October into an epic horror story Logan and her friends might not survive.
Especially Logan.
For if Sam has his way, he will not be returning to his realm alone. And in the end… doesn’t death always win?