Most of the novels are made to stand-alone, though character and world lore grows. Of all the reading orders, I think this path is my favorite - you can decide if you want to go start-to-finish with a particular theme (e.g. all the Rincewind novels), or if you want to read them semi-chronologically (first few Rincewind, first few Witches, first few Watch, etc.). There's no wrong way to do it though :)