I would recommend any Discworld book wholeheartedly, anything with Rincewind is hilarious (The last continent is a favorite of mine), also I think Moving Pictures is pretty interesting commentary on modern entertainment. I read them all over a decade ago and some of the lines I remember still make me chuckle. EDIT: Also the movie(s) Going Postal are great..."The Smoking Gnu" :)
The main problem with Rincewind is that the entry point for his story is The Color of Magic+The Light Fantastic, which as the first two Discworld novels are much weaker than later books in the series. Guards Guards is just a much better first book to read, that or Equal Rites is more representative of the quality Discworld would come to have.
Then again my first Discworld novel was Making Money and I loved it even without context (and the “Industrial Revolution” sub-series starting with moving pictures remains my favorite to this day), so you could probably just start at Sourcery and go from there anyway.
Completely agree on this point. The first two Discworld novels, while still hilarious, take being a high fantasy story much more seriously than the later stories do. I'd go as far as to argue Pratchett still hadn't found the "discworld voice" in those first two books.
