I've finished Heart Blade, and I've bought 2, one as a gift to my daughter. Here's the review I published on Amazon U.S.
This is the first Y.A. fantasy I've ever read. I'm four times the age of the typical Y.A. reader and my chosen genre is military S.F., but I thought this might be a book I could read and discuss with my daughter. I was very wonderfully surprised at the quality of this book. There is action from the very beginning. There is no gradual wind up. Perhaps a seasoned Fantasy reader might pick up some tropes and understand the difference between a Guardian, a Witch, a Werewolf, a Demon, and a few others, but I did not. But that doesn't mean I was lost. Juliana Mills has done a masterful job of mixing in the necessary information along with moving the plot along so there were no long sections of explanations dragging things down. I also suspect that she's given these characters strengths and weaknesses not ordinarily associated with this type of character. I very much liked the contemporary setting and the way the way she tied the supernatural characters into the modern world in a believable way. I'm planning on reading the next book. I want more information on the Covenant that's behind the way the supernatural characters relate to one another. This is clearly the beginning of a series, There is talk about four blades, so I would suspect a four book series. But this does not mean that this book doesn't have a meaningful conclusion. It does. I am very impressed with this book and world recommend it highly.
(So why only 4 stars? I do not ordinarily give 5 stars. I save 5 stars for a book that I feel is one of the best half dozen or so I've ever read. A story outside of my genre is very unlikely to receive 5 stars.)