I hadn't come across his author before but enjoyed this action-packed book (3rd in series but succeeds as a stand-alone). The writing was very immersive, and it seemed like the author knew the streets of Sofia in Bulgaria very well indeed.
The main character, known simply as Korso, is an independent operator available for hire to 'find things' and didn't particularly mind which side of the law he stood on, because he had his own moral code. There was a fair amount of blood, murder and deception, and our hero had plenty of technology at his disposal, along with a healthy distrust of everyone, including his own team.
The plot hinges around the development of a glaucoma drug which has the fascinating side-effect of enabling the user to see clearly in the dark for a temporary period (6-7 hours). A scientist is murdered after refusing to give up the formula and location of the prototype tablets. I felt more could have been made of the prototype plotline in a practical sense, but the story was basically about the hunt for them by the various players involved. The ending contained a surprise.
I would recommend this book to fans of action / adventure / spy novels.