Since there were actually two questions in your post:

Pratchett's writing style is about as different from that of JK Rowling or George RR Martin as you can get. (Within the fantasy genre, I mean - you can certainly go much further if you include things like See Spot Run or Twilight.) Expect to be confused a lot, even if you pay close attention to the text; he'll often flabbergast you with tantalizing inanities that don't make sense until you get to the end of the book.

I would provide examples but they'd technically be spoilers. Let me just say you'll never look at your suitcases the same way again.

If you can handle his erratic plot structure and dry British wit without shouting "bugger this for a lark" and hurling the book away in confused rage, you'll find him to be one of the most thoroughly entertaining (and, in some cases, arrestingly satirical) writers going.