"Trail of Dead" is (apart from the title which I think is rather dull) is an improvement on "Dead Spots", book 1 in the series. Melissa Olson's writing is more confident and assured, the plotting is tighter and more complex and the world building is a little bit more subtle.
In "Trail of Dead" I actually started to like Scarlett Bernard and understand the impact that she has on those around her. She's come out of her "I'm doing this because it's the only thing I'm good for" trance and started to think through her life. It turns out that she's brave and, in her own way, driven by a sense of honour and a desire to help those she cares for.
Her bête noir and former mentor, now a scary bat-shit-crazy vampire is an excellent villain to his and boo at. She makes the other monsters that Scarlett works for: vampires, witches and werewolves, seem positively civilized.
The "shall I choose the gorgeous and righteous cop or the totally devoted werewolf surfer-boy" trope could have become a little tired - too Stephanie Plumb for my taste - but Olsen pulled an original plot twist that saved the day and kept everything a bit more plausible. I do wish she'd stop telling me that Jesse smells of oranges and Armani, it doesn't sound an attractive combination and it became a sort of leitmotiv that was played every time he and Scarlet were in a scene together.
The concept of a "null", the original idea around which the series is based, continues to develop at satisfying pace that shows progress but hints at more to come.
I'm confident that this will turn into a fun series. I know the third book is out but I'm waiting for the audiobook to be available.