Mercy was rather stunning. Honestly, it took me quite a while to get past the first 50 pages. I just really wasn't in love with the main character, as she seemed rather - well - evil. Not outright, "I kill puppies" sort of evil, but certainly not nice. But I kept going, and I am so very glad I did!
There was a point, about 100 pages through the novel, when I knew I was going to love this book: it's when Mercy - as Carmen - sings her heart out. It was a show stopper, and it practically stopped mine. It was just glorious- I could almost hear the music through the pages - and rather indicative of the ethereal quality of the entire novel. If I had known Mercy had this musical element, I would have made my way through those first 50 pages a lot sooner!
Although Mercy begins as a rather apathetic character, as she becomes more involved in her human's life, I really started to like her. She is really difficult to describe... partly because I don't think she used to be a good "person". She's a self-aware adult in one way, but her lack of memory has given her room to change for the better. As she grows into her new body - Carmen - she really starts to develop into someone new.
In fact, even though this book has about 5 mysteries going on at once and a few romances that leave you begging for more action, Mercy is really all about Mercy. The singing, the murder, the hot-human!boy, and the bizarre supernatural powers are all just tangential to Mercy's development.
I've read Fallen and Hush, Hush (oh, if only I were ethically capable of burning a book). Although both were Angel YA, they both lacked that otherworldly quality of angels - staring random "insert paranormal creature here" heros. I don't mean a religious quality - I am the biggest atheist in town - but that feeling of something powerful that you can't begin to imagine. Mercy had that quality in spades - there was no doubt in my mind that she's an angel. Powerful and inhuman and, often, cruel.
So, I really can't wait for the rest of the books in this series - the nature of Mercy's condition will make the next book VERY interesting.
Bottom line? I really enjoyed Mercy for it's tough amnesiac of a main character, it's show-stopping choir performances, and it's rather subtle-yet-star-crossed romance. I'd recommend this book to fans of the Wicked Lovely series, as they both have that somewhat ethereal quality about them.