Do you read any Anne McCaffrey ?. If you have read the Pern series, the Wyrmberg parts of Colour of Magic will just slay you with laughter. I have always maintained that referential humour is much more funnier than the out and out gags. Which is why I like Simpsons more than I like Friends or why I suffer Southpark's vulgarity [read Reductio Ad Absurdum or Simpsons overload - maximum Homerdrive]. Ok, so here's the unique parallel. The dragon lady in Pern is called Lessa, all the male dragon riders have a ' in their names - like F'nor, F'lar. So Discworld's dragon lady are called Liessa, dragon riders called K!sdra, Lie!tt (Dune ref ?). Anyway, I thought the Weyrs of Pern vs Wyrmbrg was too similar to be left alone.
Light Fantastic has wordplay is what I'd call very interesting. Sort of at par with the H2G2 "Like being drunk" quote The part about the talking trees, for example.
'Trees,' said a voice out of the darkness, high above. It possessed what can only be described as timbre
Or the intimate knowledge that the author shows about science (a trait shared with the one and only). For example, the knowledge of special relativity in the following paragraph betrays an education in the sciences or at least an interest in them.
And the knife left Trymon's hand at such speed that (because of the somewhat sluggish nature of Disc light) it actually grew a bit shorter and a little more massive as it plunged, with unerring aim, towards Galder's neck.
Read relativstic mass and Lorentz Equations for an idea of how complicated the mass and length transformations really are. Though interestingly, at velocities a lot lesser than C, all these equations can be reduced to their Newtonian forms. All of Relativity could be called as a fine-tuning of what Newton put down in his laws.
All in all, nice book to read. I absolutely recommend it to anyone with a night to spare. Just don't miss all these oblique references. Watch out for the one with the rescued virgin, the hardware consultant who's flying in a new stone for the druid's broken circle or the description of trolls (water and rock both) - even the reflected-sounds-of-spirits-underneath.