I've only read the first ten or so books of the Discworld novels -- so far, I hasten to add; I will read them all! -- but I do love the Rincewind books (I love that coward
) and I think my favourite book is possibly
Sourcery. Mind you, I also really enjoy the Witch books. Granny is awesome and Nanny Ogg is hilarious.
But then I also liked
Mort because DEATH featured quite heavily in it...
You're right, it's very hard to choose!