N.B. My first review of this book gave it four stars, which I changed to five stars after realising that clues were hidden in the book.
As with the previous reviewer, my first reading of this book left me a bit confused, as I could not see where the plot was going. However, a second reading of selected bits clarifed it. In that respect, I would say it is a lot like "Night Lost", the story of Gabriel Seran and Nicola Jefferson, from the Darkyn series.
Due to the unexpected identity of the hero of this story, I won't name names. However, I did understand how he came to be what he was, but the reader perhaps needs to be familiar with what happens to the GenHance character in 'Shadowlight' to understand how this could have occurred.
Originally, I was going to give this book four stars, because I thought it was a bit confusing. Ms Viehl has written a cracking story, and she does try to explain how things might have happened the way they are, without the reader having to have read any of her previous work. The loss of a star would be for the initial confusion. However, on a second reading, the book is peppered with clues as to this individual's identity, the most intriguing being when he and Lilah are discussing a name for him, and she suggests her grandfather's name. He is most emphatic that he does not wish to use that name. I won't say what the name is, but it is a major clue. Equally, tne start of the book gives an indication as to characters who may be involved, but it requires some consideration to work out the link. His recognition of a a weapon used by another character is a further indication. So several clues, but you have to realise what they are, and put them together so that you don't end up being totally gobsmacked by his identity at the end of the story.
I would advise that you either read this slowly, or read it at least twice!