Evil in general does not sleep, and therefore doesn't see why anyone else should.

Vimes stalked gloomily through the crowded streets, feeling like the only pickled onion in a fruit salad.

I'm trying to have a moment o' existential dreed here, right? Crivens, it's a puir lookout if a man canna feel the chilly winds o' fate lashing aroound his netheres wi'out folks telling him he's deid, eh?

When all else failed, she tried being reasonable.

Ponder just let it happen. It's because their minds are so often involved with deep and problematic matters, he told himself, that their mouths are allowed to wander around making a nuisance of themselves.

Now he knew: They were real. Who’d make up a thing like this? Okay, one of them was a cheese that rolled around of its own accord, but nobody was perfect.

The Library didn't only contain magical books, the ones which are chained to their shelves and are very dangerous. It also contained perfectly ordinary books, printed on commonplace paper in mundane ink. It would be a mistake to think that they weren't also dangerous, just because reading them didn't make fireworks go off in the sky. Reading them sometimes did the more dangeous trick of making fireworks go off in the privacy of the reader's brain.