Wooo, thanks! Major Discworld fan here, yay for art!
And ya, you can read them in pretty much any order, although reading them from start to finish makes the characters grow better. Don't forget the three Tiffany stories and the several short stories (which are available free on LSpace) - Sea and the Little Fishes (which is awesome), the High Price of Living (fantastic), and the oddly out of character Carrot in Theatre of Cruelty (so-so).