The first one I ever read was Sourcery, followed by Monstrous Regiment. Lost count of how many I have read, although I think it’s pretty much all of them. My list of favourites includes Hogfather, Moving Pictures, Snuff (purely because of the amazing Austen theme that runs throughout the whole book if you spot all the references)and Going Postal. My absolute favourite has to be Maskerade. 1) I love the witches. 2) I love Phantom of the Opera, it’s my favourite musical. 3)The rest of the Andrew Lloyd Weber references are brilliant.
And I think that Terry Pratchett still being able to write his brilliant stories is nothing short of amazing.