The Host by Stephenie Meyer

Featuring one of the most unusal love triangles in literature, The Host is a riveting and unforgettable novel about the persistance of love and the essence of what it means to be human.

Melanie Stryder refuses to fade away. Our world has been invaded by an unseen enemy that takes over the minds of human hosts while leaving thier body intact. But Wanderer, the invading "soul" who occupies Melanie's body, finds it former tenant refusing to relinquish possession of her mind. As Melanie fills Wanderer's thoughts with visons of Jared; a human who has avoided invasion and lives in hiding, Wanderer begins to yearn for a man she's never met. Soon Wanderer and Mealnie- reluctant allies- set off to search for the man they both love.