Discworld was always in change. The first two book were not only a tale of Rincewind, but also of the end of the golden age of fantasy. Since then Discworld has advanced very considerably both at a technological and a social level. The arrival of steam is, I think, a very expected move in the ever changing world. Indeed automation and machines have happened before (though a certain, rather bony, character put an end to the advance of the farming industry in one book).
I've got the hardback sitting here, though I've not yet read it. I can agree that Making Money almost felt like Going Postal re-written in some ways, though was still a solid fun read. I'm sad to read that many feel that Rising Steam is falling apart some (its a view I've seen mirrored in many communities). Sadly I think Terry had great plans for the evolution of Discworld and that its a great loss to us that we might not see the end (though my honest view is that there likely was never going to be an end).
