Pratchett's books just seem to get better and better, but this one was sort of a small letdown for me.
Let me say at first: The plot, the characters (especially them), the jokes, all this is great, perhaps even the best this far.
However, it's inevitably a very preachy book. When the message is so obvious and unsubtle, it can mar the best plots.
The big bad guy here is the Grand Trunk Company; legal theft, sabotage, obese and ridiculously helpless capitalists; it's not hard to spot. On page 72-73 Lord Vetinari delivers a political monologue at almost a whole page lenght. After his clonclusion, the book goes:
"Lord Vetinari opened his eyes. The men around the table were staring at him."
Through the preceding books, I've got to know Vetinari as the quiet, confident ruler who pulls the strings to make Ankh-Morpork run, but here it seems to me he's simply showing off. Why does he do that? He doesn't need to show off, he doesn't need to impress other people.
Then, near the end, there is this "message from the dead people", which we know was written by Moist. There's context of the message; the idea of "Sending Home" and other eerie clacks mythologies. But the actual text of the message sounds like a statement from a French student union in 1968, or something like that, with all its polemic agitatiton.
Some people say Going Postal might be a satire on Ayn Rand's Atlas Shrugged. That would certainly explain why all the opponents (except Reacher Gilt) appear to be political strawmen. It'll also explain why the good guys feel the need to deliver long politcal speeches.
But I feel that Discworld by now has abandoned the specific parodies to instead work on its own characters. Is he then using a dear character like Vetinari for this purpose? Oh well, I don't know.
To sum it up, Pratchett has in this book a rather obvious agenda against big, centralized capitalism/market liberalism. On which I agree with him: These big corporations hurt both individuals and society. But when his criticisms of corporations surface this openly and indiscreetly, it's hard not to be conscious of them. Any reader who agrees with market liberalism can easily root out the political message and ignore it.
Here's the problem: When it comes to capitalism, Pratchett simply isn't very good at satirising, as we have seen already in Johnny and the Dead; it tends to deteriorate to stereotypes and clichés about evil, fat men in suits who instantly panic whenever people speak up against them. He makes market liberalism seem silly and harmless, which it most certainly isn't.
And this is really sad, as Pratchett seems to make such good observations on all sorts of other stuff; heroism, war, nationalism, revolutions, religion, social issues, and so on.
But capitalism? Leave it to Jasper Fforde!