Keith Brooke 
alt.human (aka Harmony) [EPUB ebook] 

The aliens are here, all around us. They always have been. And now, one by one, they’re destroying our cities. Dodge Mercer deals in identities, which is fine until the day he deals the wrong identity and clan war breaks out. Hope Burren has no identity, and no past, struggling with a relentless choir of voices filling her head. In a world where nothing is as it seems, where humans are segregated and aliens can sing realities and tear worlds apart, Dodge and Hope lead a ragged band of survivors in a search for the rumoured sanctuary of Harmony, and what may be the only hope for humankind.