(Putting the entire "Discworld Series" in as a single item is a cop-out. If you ask people, they can come up with two or three must-reads.)

I noticed that. I figured they couldn't get any consensus on the must-reads (even though everyone I know recommends Small Gods . . .).

ETA: I figured out what tipped my subconscious off: it's The Glass Bead Game. Heh.

Explain?

There seems to be a more detailed breakdown here.