3.5 
 I kind-of enjoyed the book, I think. I found Anna more interesting than Cas and in general I didn't feel attached to any character except the ghost. And I couldn't overcome my disbelief and found very weird that not only Cas but everybody could interact with Anna like she were real (and kissed her and leaned on her and, and... O.o). I felt that something was odd or out of place the whole time while I was reading, but I couldn't put my finger on it. 
 Anyway, I did like it enough to want to read the second book... What I don't know is if I want to pay for it *roll*