Speaking of postal matters, I finished reading Going Postal. Overall, I think the later Discworld books are a lot more detailed, but less laugh-out-loud funny. I was amused by Bloody Stupid Johnson's letter-sorting machine, for which Johnson changed the value of pi to be exactly three. There was also a professor at Unseen University who had taken an Early Death package, which strikes me as quite similar to Hotblack Desiato's spending a year dead for tax reasons in The Hitchhiker's Guide to the Galaxy. I guess there are quite a few similarities in the humor used by Terry Pratchett and Douglas Adams, though.
It's kind of odd that the Discworld had the Clacks, basically an optical telegraph system that bears some similarities to the modern Internet, before they had postage stamps. I guess that kind of thing can be explained by Thief of Time, though. Pratchett does a good job at explaining how modern technologies, or fantastic equivalents thereof, show up in a fantasy world. I do think the series has definitely gotten more modern over time. Sure, there are still vampires, dwarfs, and trolls. Going Postal also introduces a wild banshee, who is very different from the civilized Ixolite from Reaper Man. I get the idea, however, that The Colour of Magic was largely an attempt to create a world where science and nature are governed by ridiculous superstitious notions (the world is carried on the back of a turtle, lightning is caused during battles between the gods, cameras and watches are operated by demons). While there are still some instances of such things in the more recent books, the general feel is more organized and realistic. While earlier books had the Discworld's inhabitants actively fighting off malls, movies, and rock music, more recent introductions like newspapers and Clacks towers not only stick around, but play large parts in later additions to the series. The main villain in Going Postal isn't an evil wizard or demon, but an unscrupulous businessman. I'm hardly saying anything that hasn't been said by plenty of other people about the way the Discworld series has developed, though. I think it's good that the world is broad enough to be able to fit both madcap comic fantasy AND stories about newspapers, armies, and the postal service.
My next book to read is Lemony Snicket's The Grim Grotto. So far, I've finished the first three chapters.