The concept of an ancient being, composes of energy and immortal, being trapped in a human shell is interesting. Rachel Caine does not carry this as far (or as well) as THE HUNDRED THOUSAND KINGDOMS, but she certainly casts Cassiel as alien enough to be a compelling and unique main character. My only complaint is how quickly she becomes selfless and willing to sacrifice herself for humans, and how the cliff-hanger ending leaves littler or no resolution to Book One. The second issue is easily enough addressed, on to Book Two!