Lots of action and a unique mythology make for a very enjoyable read. 
 Darian is a Shaede, an immortal being who can fade into shadow and has increased strength and healing ability. These powers make her an excellent assassin. Since her maker vanished leaving her to believe that there were no others like her, she has been alone. She is attracted to her current business contact, Tyler, but doesn't want to risk their friendship, and more importantly let down any emotional walls. 
 Then she gets a job that throws everything she "knew" in the dumpster, sets it ablaze and stomps on the ashes. 
 I really liked the supernatural mythology at play here, and in book 1 we've only tasted some of it. 
 Darian is prickly, standoffish and cold, but she's earned every emotional wall. I liked seeing how a certain character got through to her. Also, the final battle wouldn't have been as effective without those walls.