We've added The Books of Ember to our recommended reading list (sidebar) for ages 9 & up. It is a series of young adult fiction by Jeanne DuPrau begun shortly after 9-11. Here's a fantastic quote from the second book of the series The People of Sparks:
"'You turned a crazy old guy into an enemy in less than two minutes. You did it. You've done it over and over, I've seen you: you approach people like an enemy and bam!, they turn into one, whether they were to begin with or not' [Maddy accused, after discovering she and her traveling companions had been robbed during the night by a hungry old man Casper had refused to help the day before].
'It's my policy to be ready to defend myself," Caspar said, scoling. 'At any moment.'
"Fine," said Maddy. "So now, because of your policy, we're out four cakes instead of two [we could have easily spared], and we have a lot of dirt on the rest.... If you ask me, making friends is a better defense than making enemies."