Shadow Touch, a novella by Erin Kellison, is free for UK customers in the Kindle store; should be free for US customers within a day or so. (
UK link)
Book Description
Magic
It is bleeding into our world, bringing with it banshees, wraiths, fae from the twisting forests of Twilight. But Elllie's problem is a very different kind of phenomenon. . .
Shadow
It ought to be attached to her; instead it has a life of its own. And her dark mirror image is a wild thing, willfully seducing the very man Ellie hoped could help.
Science
Cam has devoted his career to exploring the boundaries between this world and the Hereafter. But nothing could prepare him for the mischief and mayhem of a soul split in two.
Surrender
Who will give in first: the man struggling to unite two halves of one fascinating female; the shadow fighting for freedom to experience the thrill of every emotion; or the woman who is about to discover her own deepest desires?