Story-wise, there are only a few things that happen that can be directly attributed to “the light fantastic”, with the vast majority of the plot dealing with technological changes intertwined with social changes. In and of itself this is not necessarily a good or bad thing; but when you pick up a book that is part of a fantasy series, you tend to expect, well, fantasy.
On top of that, I found the actual story-telling to be somewhat heavy-handed in its parallels to modern society, with Sir Terry seeming to spend too much time telling us instead of showing us what is going on. This may in part be due to having so much he wanted to say in combination with perhaps a few too many characters, leaving this reader feeling that I never had time to really relate to any of the several important characters. Unfortunately, I also can’t help but wonder how much the writing might be affected by Mr. Pratchett’s early onset Alzheimer’s, both its effect on the mechanics of writing as well as mental processes involved.
All that being said, it’s not a bad book: I just did not find it to be an exceptionally good book. For me it was in that range where I’m glad I read it, but doubt that I would ever have any real interest in re-reading it. (Note that I am the sort of reader who is more than willing to re-read books I loved or really liked, not the sort who almost never re-reads anything.) All in all, it’s probably a must-read for hard-core Discworld fans, but if you are new to this world, I’d suggest starting out with one of the earlier novels.