Good Omens was such a palate cleanser after Irregular Witches which I had really enjoyed up until that hard left turn. Hogfather is a perennial favorite, as is Night Watch (especially relevant these days, I think), and anything with the Witches or Tiffany Aching.

I...kind of wish I hadn't read the last few Discworld books. I strongly suspect they were ghostwritten following outlines or plans PTerry wrote before his condition worsened; there's maybe one sentence out of every hundred in them that strikes me as something he actually wrote.