The Science of Discworld, by Terry Pratchett, Ian Stewart, and Jack Cohen works quite well as a bedtime/filler book. Chad’s book log entry describes the basic setup very well, so I’ll just mention a couple of things that I particularly liked.
One was a discussion of an experiment that used a genetic algorithm approach on electronic circuits, to explore evolution. After four-thousand odd generations, the resulting circuit could tell two tones apart, but in an incredibly complicated and non-intuitive manner; for instance, five of the logic cells in the circuit didn’t appear to do anything (they weren’t connected electrically to any of the others)—but if you took them out, it wouldn’t work any more. I thought this was a really illuminating example of how evolution doesn’t necessarily rely on narrativium (the power of story, which in the Discworld is one of the driving forces of the universe) and, therefore, doesn’t have to produce anything we’d recognize as a designed solution.
The other is a silly bit, as the wizards contemplate an ice age on Roundworld:
“I think it looks more like a Hogswatchnight ornament,” said the Senior Wrangler later, as the wizards took a pre-dinner drink and stared into the omniscope at the glittering white world. “Quite pretty, really.”
“Bang go the blobs,” said Ponder Stibbons.
“Phut,” said the Dean cheerfully. “More sherry, Archchancellor?”
“Perhaps some instability in the sun . . . ” Ponder mused.
“Made by unskilled labour,” said Archchancellor Ridcully. “Bound to happen sooner or later. And then it’s nothing but frozen death, the tea-time of the gods and an eternity of cold.”
“Sniffleheim,” said the Dean, who’d got to the sherry ahead of everyone else.
(Good night, everybody . . . )