My Soul to Keep (Paperback, Original)

Kaylee has one addiction: her very hot, very popular boyfriend, Nash. A banshee like Kaylee, Nash understands her like no one else. Nothing can come between them.
Until something does.
"Demon breath." No, not the toothpaste-challenged kind. The Netherworld kind. The kind that really "can" kill you. Somehow the super-addictive substance has made its way to the human world. But how? Kaylee and Nash have to cut off the source and protect their friends--one of whom is already hooked.
And so is someone else...