Burn by Suzanne Wright

BURN (The Dark in You Series Book 1) - Suzanne  Wright
Harper Wallis is a local tattoo artist, and a demon. She's good at keeping out of trouble for the most part, but when she ends up having to fight for one of her friends in the Underground things get messy when the most powerful demon around takes an interest in her. Knox is living a pretty detached life. He only has his sentinels close, and even they are afraid of him. Those who know what he really is fear him, and for good reason, but it keeps most people away. But when he finds out Harper is more important to him than either of them realized life just got a whole lot harder for both of them. 
Burn was a very interesting start to this series. The author brings us into a whole new world of different kinds of demons, and it extremely interesting. I really did enjoy this story. I liked both of the main characters, and I look forward to reading more.
The only downside to this one was I felt Harper and Knox's relationship went kind of fast once they got together, and that sort of made the story a little frustrating at times. Other than that I did really like it, and am excited for more.