I found Vicious, easy to like. About two super powered dudes, with slightly disappointing abilities, fighting their inner demons while seeking vengeance on each other. It jumps between the past and the present. The story starts with some low-grade Secret History vibes mixed with a superhero origin story.  But overall, it felt like a 90's or early 2000s thriller. While I would categorize it as urban fantasy, the book felt more like the novelization of a comic. I liked the morally grey characters, but I wish there was more depth to their motives. This story could have been bigger in scope. However, I can't deny that I enjoyed the read. 

The audiobook was decent, not the best, but no faults to really complain about. 

I know this has a sequel and plans for another, but I think you could read this as a standalone. 

I would recommend this to people who like quick, easy to read books. Or to someone who's into comics and graphic novels. It might even be a must-read for readers who love being in the head of the villain.