I'm a huge fan of Pratchett's Discworld books, but I have to say that this is not the best of the bunch. Maybe it's that the main character, Going Postal's Moist von Lipwig, is a thoroughly reformed scallywag. In Postal we all knew that he was going to realize that he had a heart of gold and do the right thing, but it was fun watching him discover it. And the plot is clever enough, but maybe just a bit too clever, with too many of its gears exposed. It's not bad -- I LLOLed* a few times -- but I've read better from Pratchett.
* It's well documented that LOL, originally "Laugh(ed) Out Loud", has become completely devalued. So I'm introducing LLOL -- Literally** Laughed Out Loud.
** Of course, since literally is also already devalued from its original meaning, I may be fighting a losing battle here.