Reading this book was a strange experience. 
 For one, I felt the urge to read two other books while I did not yet finish Vicious. I just couldn't stay in the story too long. It bothered me. I did not really feel sympathy for the main characters (Eli and Victor) and other characters I could eventually appreciate came in later in the story or we were told their story later on. So, I struggled for almost until two thirds of the book to be interested in the story and by then I assumed what will happen and the rest was just a long wait. 
 For two, after I finished I just had to think about why I did not really like this book and at the same time why it intrigued me. 
 After thinking I came to some conclusions about what disturbed me and what fascinated me. 
 Let's begin with the things I found not so good. What did not work for me personally was the writing style with the chapters that jumped from the near past to 10 years ago and then back again to the near past and al this to end the book with the present. This could have been a good thing but in this particular story, I just did not like it. I just found it a little cheap to build mystery around the characters. 
 Then, the characters did not really work for me ether. Victor, the main character, was supposedly not that bad as Eli the villain. They were supposed to represent two kinds of mental illnesses or psychopaths. On the one hand, Eli was the full blown crazy man who becomes obsessed, justifies himself with his obsessions every time he hurts someone and this even gives him pleasure. He basically became a fanatic. On the other hand, Victor was supposed to be bad too, but not as bad as Eli. Victor learned to control himself to be able to hurt as few people as possible and also learns himself to know which feelings he should feel if hurting others (like guilt). So, these two people lost their moral emotions (empathy and guilt) but where one chooses to act as an exterminator the other chooses to remain as human as he can. I guess, this was the premise of the story. But I found that Victor was also difficult to like because he was just as obsessed as Eli but where Eli had his ideology Victor was just obsessed about revenge on Eli. Both were ready to do bad things to obtain their goal, but at the same time they both had one moral rule, do not kill innocents if you can. 
 I just couldn't like Victor for these similarities with Eli and also because he was ok with using and manipulating people to have his way. He was not after Eli because he wanted to stop him doing the bad thing he did but because he wanted revenge. 
 As Mitch said to Sydney 
 "There are no good men in this game." 
 This sums up really well why I couldn't get into the story but also why I was fascinated by it. The fact that you can be morally bad in many ways or good in many ways depending on the perspective from which you're looking at the situation is thought-provoking. Also, the question, is it ok to fight immorality with other immoral measures is interesting and important to ask. Questioning morality is a good thing to better understand that the world is complex and there are not only good guys and bad guys. There are all kinds of vicious... 
 It would just be a shame to think one have to choose between one: 
 "Your power is unnatural [...] It goes against nature. Against God. [...] this is for the greater good." 
 or the other: 
 "Perhaps he should feel responsible for unleashing a monster on the world, [...] but as he stared down into the faces of the dead, all he felt was a kind of quiet joy, a vindication. He'd been right about Eli all along."