Rebecca Lim: Mercy: Book 1 [2010] paperback

An electric combination of angels, mystery and romance, MERCY is the first book in a major new paranormal series.

There’s something very wrong with me. I can’t remember who I am or how old I am, or even how I got here. All I know is that when I wake up, I could be any one. It is always this way.
There’s nothing I can keep with me that will stay. It’s made me adaptable.
I must always re-establish ties.
I must tread carefully or give myself away.
I must survive.

Mercy doesn’t realise it yet, but as she journeys into the darkest places of the human soul, she discovers that she is one of the celestial host exiled with fallen angel, Luc. Now she must atone for taking his side. To find her own way back to heaven, Mercy must help a series of humans in crisis and keep the unwary from getting caught up in the games that angels play. Ultimately she must choose between her immortal companion, Luc, and a human boy who risks everything for her love.