There main character, Rain, is one of the most unique characters that I've encountered in science fiction/fantasy. She's a trickster spirit who was captured by a shadowy government agency that, through some technological means, managed to split her persona into a plural system of several different people/persons in one person with limited shape shifting powers.

Ancient spirits, plurality, shape shifting, secret government agencies: I've not read anything like this before.

In the book, she's trying to escape this agency which has been forcing one of her personalities to work as a soldier/assassin.

The central personality, Rain, was formed to understand herself as human, rather than an ancient spirit, and the book details her quest to hold onto this humanity as the machinations of government agencies, the spirit realm, and her other personalities war with her for control.

There's a LOT going on in this book.