Let's just save everyone time:
Everyone except JSWolf: There are multiple good starting points to read Discworld, don't feel like you have to read them in publishing order.
JSWolf: The
only way to read the Discworld novels is in publishing order and this is the hill I've decided to die on.
There, we can dispense with the 20 or so comments of
this time around and continue on with free & discounted ebooks as usual.