I agree that "Moving Pictures" would work on itss own but I think "Soul Music" won't work quite as well if you don't already know a few things.

But other ones that work on their own would include "Small Gods". "Wyrd Sisters" would also work, especially if you wanted to "read a few in the middle" before commiting oneself! "Mort" would work for the same reason.

I agree that the latest ones need prior novels. "The Truth" for instance, is just not as good if you haven't already encountered Vetinari numerous times. Or Ankh-Morpork's Guilds. Or Vimes. Or Slant, for that matter. Or the Clacks. Or even the Bursar.

Wade.