Jaci Burton's "Demon Hunter" series is very enjoyable, each book written in such a way that it can be read on its own without knowledge of the previous ones. The Darkest Touch, which follows on from Surviving Demon Island and Hunting the Demon, follows twin sisters Angelique and Isabelle as they find themselves immersed in a whole new world, that of demons and the fight against them. Angelique and Isabelle, who first appeared in Hunting the Demon, are archaeologists; the initial meeting between Angelique and the male love interest of this book, Ryder, took place in that book.
In this book, we follow Ryder as he searches for the missing Angelique who has stolen the Black Diamond, a special artifact that the demons want. When Ryder finds Angelique, he discovers
that the demons have also found her. Can he keep her safe - and, more
importantly, can she come to terms with some insights into her history and with
the possible evil nature of her twin?
Alongside the primary romance is a secondary one between Isabelle and another of the demon hunters which isn't resolved in this book.
That will presumably be the focus of a future story.
Jaci Burton measures her pacing well and writes a certain amount of characterization. This British reviewer found the dialogue between the lovers
a little too sappy to stomach, but overall it is an interesting story with plenty of action.