In Dark Heart by Margaret Weis and David Baldwin, Lord Justin Sterling is an immortal who serves a mysterious being he calls master and, for whom, he kills repeatedly. Sandra McCormack is a Chicago cop who has survived the abuse of her ex-husband and is investigating a string of violent and unexplainable murders. Eventually, their paths cross and their lives are changed completely.
It took me a long time to get into this book. It often felt like the two authors had different styles which didn't always mesh. As well, the fantasy and thriller elements often seemed to be competing for precedence - I found myself wishing the book would decide whether it wanted to be one thing or the other.
However, I am not one to give up easily on a book and, about half way through, I started enjoying it. The story was interesting and the idea of dragons in the modern age was intriguing. There's lots of action and, although there is some romance, it didn't bog down the story. According to the cover, Dark Heart was the first in a series titled Dragon's Disciple and I looked forward to the sequels, especially as the book ends on something of a cliffhanger.
However, I soon discovered that David Baldwin was Margaret Weis' son and he has, sadly died. Weis has since said that the story was mostly David's and she will not continue it. This is understandable but it does leave the story unfinished, something you might want to consider before reading it.