It's rare to read a superhero novel, rarely still for it to be good as fight scenes don't work as well in books as they do in comics. Thankfully the Powerless series of which Killing Gods is the second book doesn't rely heavily on action but rather the personal and social issues of being a powered individual after the registration act.
Killing Gods isn't directly dependent on powerless book before it to know what happened. That being said I would recommend the first book as it explains how Martin and Hayley became a team more and the plot focusing on Martin's old team mates is original and full of surprises.
Killing Gods focuses on a powered baby who can create anything out of thin air and attempts by a hero church, social services and an antihero group to get the baby from his parents. By having so many different characters, Tony explores the different ways powered heroes effect and are affected by politics. Several of the laws against heroes are different to any I've come across before like any powered child needed to be examined and perhaps took off his parents before anything goes wrong (the first of several points in the book that elicited an emotional response from me). These laws and the varying viewpoints show that Tony is confident enough in his world building to explore it in detail rather than leave it open to interpretation.
Although you want Martin to save the baby throughout the book many of the characters have good motivations so even though you can't agree with their actions you can understand them. This is a mark of a good book as it makes you wonder what you would do in a certain situation if you had similar circumstances. In addition various philosophical questions are posted like how can you ban someone for using their powers if they’re not harming someone, nature vs. nurture, should you wipe off someone's severe criminal record just for registering. There's not much focus on Martin and Haley which is odd considering they are the heroes of the story but there's bits were you can see the teacher relationship between the two. Martin's social anxiety and need to avoid conflict is shown several times. But I'd like a bit more from Haley's viewpoint as we rarely know what she thinks of Martin. I'm addition I'd like to know a bit more on how she struggles being a police officer and not using her powers. Tony has done a comic on this but that seemed a bit episodic. Overall I'd give this book 8 out of 10.