As I think I said earlier - Terry seems to have used this book to say goodbye to the 'old' Discworld. I think the 'new' Discworld, arguably started in the previous book, The Truth. It's almost as if the time period on DW has moved from Regency to Victorian and subsequent books are somewhat more 'modern' in their outlook.
The Gods don't really play a significant part in the books after this one and neither do we really see anything of heroes. Those are parts of the DW world that Terry is laying to rest.
The wizards have been becoming more scientific in their approach to the world and machines are playing a larger part.
We've probably seen the last of Leonard too.