You will need to believe that the main character knowingly makes many bad decisions in this book to really enjoy it. I thought the writing was excellent, and I thought the main character was a good character, however I could not accept the course plotted for the main character by the author. The plot is driven by bad choices. Very bad choices. Choices that any person most likely would not make. And that, to me, should not be how a plot is driven. One bad choice would be fine - but in this novel bad choices are an epidemic.
The main character, Jack Griffen, could have gone to the police in the first few chapters. Instead, he bumbles around and makes odd phone calls and impersonates an immigration officer to speak to a young woman who was assaulted while jogging. Why? I honestly don't know why. Are we to believe he could have unusual trains of thought due to having a nervous breakdown years ago? I'm not sure, but that hardly seems like a reason for how he acts during this book. I found his behaviour and decisions very odd.
The plot itself is OTT, but that's fine for a mystery/thriller. It's all part of the genre. The author, I think, tries to make our protagonist an unreliable narrator, but that really didn't work as intended. The villain of the piece, Hiero, did work as a character, and as the characters are written, he's probably the most consistent and best written in the story. The other characters felt incomplete.
I think this book would have best served to have a smaller scope, not make this an international thriller. We didn't need to see so much country hopping, for that did not add anything to the plot and, at times, it made the plot harder to swallow.