"He who fights with monsters should be careful lest he thereby become a monster. And if thou gaze long into an abyss, the abyss will also gaze into thee"
- Friedrich Nietzsche ; Beyond Good and Evil (1886)
Not that Iris doesn't deserve every bit of it, but Liesel's going pretty dark herself towards the end, there (it would have been fine, if not for that little look of schadenfreude on the last page).