I don't have much experience in graphic novels, but this is my point of view. This is a novel about a zombie apocalypse, but it's also so much more. In the introduction, Robert Kirkman explains that he was interesting in portraying a different zombie story. The psychological aspect was important, which is evident in the main character's change through the story, in a time that demands great, and not always kind, measures. That is one of the most interesting themes in the book. The story is not first and foremost a story about the apocalypse, but a story with psychological dimensions.
As for the layout, the book is well-detailed and carefully crafted. The pictures are really artful, with everything from the shadows to the characters face expressions.
However, there are some minor distracting details, from a gender perspective. The division of responsibilities in the group is interesting. Everyone should benefit from learning all kind of skills. That is necessary since no one knows what the future holds. Donna mentions that the women clean the clothes because of their gender, and she is onto something. Unfortunately, she is portrayed as a whiny, bitter woman and Lori - who doesn't question anything, and equals the proper woman - is protesting against Donna. Upholding gender differences don't belong in this kind of situation. Of course, the most skilled should do the work. Man or woman. Rick should be hunting. He is a police officer, accustomed to danger and weapons. But Andrea turns out to be a rather good shot, as well. Why make a big thing about it? Women can be heroes, as well.
Another thing worth mentioning is the quote that Dale "deserves" two women - of course young and beautiful - living with him, indicating something, but Dale merely states that they are only friends. Why not let them do whatever they want together, and neither honor or condemn it? Perhaps some indulgence is necessary, but what is the meaning of portraying women's purpose as being a reward for men that "deserve" it, without consideration to the women's needs? Why is it never the opposite, that a women deserves two young, beautiful men? I don't think the characters have these remarks in the tv-series, so I'm biased since I watched it before I read it.
When it comes to the structure of the characters in the book, the obvious leader, Rick, is a good man, most of the time, but the fact that he appoints himself as the leader of the group, only questioned by Shane, is another silent rule. Kirkman had a possibility to explore gender equality, but he passed. It's evident the book is written for men. However, the most irritating character is Lori. Why is she so boring and unlikable? She and Shane knew where Rick was and thought he was safe, but even so, didn't come back for him. When Rick woke up, he was crazy about finding his family. Why couldn't Lori be the same?
The most interesting theme in the book is about humanity and responsibility in this kind of situation. To what extent are we supposed to take care of each other? How human are we? In many ways, mankind is worse than the walking dead because people are responsible for their actions. The book is as much a social commentary as a zombie apocalypse story. It's fascinating to enter a world where the normal laws don't apply anymore. This is the first book, and just the beginning, but Rick's gradual change in the series is a way of showing how much our ordinary lives are driven by laws, social structures. It's easy to follow the laws and be humble and empathetic when everything is normal. But when the society has collapsed, some other, more primitive, factors about survival instinct surface and become significant.