"I am a socially awkward mandork." (1.1)
This is our first line in chapter one, which lets us know right off the bat that having a reputation is important to Nick…and that he doesn't have a good one. Although we can think of several things worse to be than a "mandork."
"If anyone sees me in this, I'll be an outcast relegated to the loser corner of the cafeteria." (1.3)
We wonder if the loser corner of the cafeteria is cordoned off from everyone else. Is it separated by a moat? Who are these losers in the corner? Nick acts like every single person in the school is popular except for himself.
"I have enough trouble coping at school. I'm pretty sure killing three members of the football team when we're coming up for a championship would ruin my rep forever." (5.113)
Even when zombies are on the loose, Nick is worried about his reputation at school. When you're a teenager, reputation is everything.
"That's exactly what I'm talking about. That's the evil that's seducing you. […] You have to let that anger go before it's too late. Vengeance always turns inward and it will consume you until nothing's left by an empty hole that nothing can fill." (16.40)
A key conflict in the book is one that Nick isn't entirely aware of. It seems that if he lets his anger and vengeance control him, then he will become a Malachai, which is this book's equivalent of going to the Dark Side with Darth Vader. Ambrose, who is Nick from the future, is trying to guide Nick away from this violent path.
"Now take your vengeance on the ones who've mocked you. Kill them and eat their brains." (17.159)
Here we see the bad guys baiting Nick to come to the dark side. They want him to wreak vengeance against one of the bullies who's got it out for him. Nick's future pivots on this one violent act, and luckily, he doesn't commit it.
"We take care of my mom first—she's my number one priority. I have to make sure she's safe." (15.100)
In case you haven't caught by this point, Nick's mom is his number one priority. He risks his own safety to make sure she's safe, and it pays off.
"One day, Mom, I'm going to buy us a really nice house." With really nice stuff in it. (1.33)
Money can't buy happiness, but it can buy stuff. And Nick thinks that stuff will make him and his mom even happier.