The idea is the key to how this book works so well. The amalgamation of all the creatures that have ever terrified you, all put into one world and with seemingly one person to protect the humans from them. It is a really great concept, and certainly not one that has been thought of before. Yes, a few may have Kali has no idea what she is and why she feels the need to hunt the 'things that go bump in the night', and so the entire story has undercurrents of this persistent question which brings huge revelations in the latter stages. In the meantime, the main action is in battling preternatural things and trying not to get killed. It all culminate with one whopping twist. You can kind of see it coming, but not until a few minutes before it happens.
Character-wise, I thought Kali was a wonderful voice, with just the right amount of sarcasm and abnormality that you immediately warm to her. The book is in first person, so you truly get the sense of who she is as a person as well as the deep sense of loneliness that she has at the beginning. However, it was actually her new friends, Skylar and Bethany, who I liked the most; Skylar for her absolute vivacity and bravery, and Bethany for everything she ever says - if you want a sarky / snarky comment, she's your girl.
A surprising and captivating read, if only it was longer and better developed. But this may be because it was meant for teens rather than adults. I am really hoping for a second book that delves more into the world and the other preternatural creatures. 8 out of 10.