Simply brilliant. The jokes, puns, word play, and intelligent idea skirmishes were so fast and furious I could barely keep up. I loved it. I think it's one of the best. I really loved the camels and the names they have by custom. Hilarious. Forget the arguing about whether it's four stars or five, or if the fabulous irony is post modern, sit back and have fun listening.
Of course, that's an easy review to write. Pratchett takes all of human history and mushes it together in this crazy place called imagination. Sit back and enjoy the ride.