In volume 4, our group of survivors are settling into the new normal. The children are so used to seeing zombies around that they aren't even scared of them anymore. That's all they know. That's their normal. 
 The world is over and not coming back. It's all an uncharted path now. The old ways of thinking about what it means to be in a "society" no longer apply. Humanity will only get you so far in the face of annihilation. You must also embrace your primal savage side if you want to survive. We see this in Rick. He finally comes to terms with loosing all hope and it makes him into his most nihilistic and most powerful self. 
 Even after the apocalypse some things never change. Relationship's still have problems. Just because the apocalypse happened, it doesn't mean that people don't break up or cheat anymore. However, considering the dead are now trying to eat the living, everyone's emotions are teetering on a particularly steep cliff to say the least. What once could be healed with a pint of ice cream and a good cry now festers into something deeply dark and disturbing. When people are already hopeless, it doesn't really take much to have them fall - or purposefully step - off that cliff. 
 The apocalypse brings out new sides of people. Some search for a savior. Some fold into themselves with denial. Some rise to the top and become the leader. But none of this changes the fact that it's still a world of borrowed time as they all wait until it's their turn to join the walking dead. 
 (view spoiler)[ When they cut Allen's leg off to try to save him... I literally said "Holy Moley!" out loud. It's ambiguous as to whether Allen died because of the bite or due to blood loss or something. Michonne seems a bit underdeveloped. Like she just showed up and fucked things up. I see potential in her becoming an interesting character. She's just not there yet... (hide spoiler)]