I am a HUGE Terry Pratchett fan, so I was glad to see this! Thoughts:
It’s not in this book but when Glenn finds out about L-space I think he will lose his mind.
I’ve read all of Terry Pratchett’s novels and not every novel is for everyone. I can’t see anyone who isn’t at least familiar with the Lloyd-Weber version of Phantom of the Opera liking Masquerade and I will not be rereading any of the novels featuring Rincewind and the Luggage. [Note to Brent: your niece might like Pratchett’s Tiffany Aching books.]
The lack of plot in the first part of the book doesn’t bother me at all. Like many of the other Diskworld fans I know, I’m happy reading for the humor and the character interactions. As for the elves arriving late in the book, two things: First, there is a build up to their arrival. It’s a slow burn, I’ll give you that. However, it’s not like the plot kicks into gear out of nowhere. Second, the Elves are so OP that I’m not sure how much more of them would have served the story. As an aside, with their mind control and casual sadism I found that they now make me think of Kilgrave from season 1 of Jessica Jones. That being said, I have no idea if David Tennant has ever read this book or not.
The Diskworld books are, in part, parodies of fantasy tropes, so it makes sense that the elves, without their glamour, are small, ugly and vicious. Beyond the parody, Pratchett is very good at weaving in elements from other books. The part about Nanny Ogg surrounding Diamanda with iron and then Magrat taking the iron away is lifted from Dracula. There’s a pretty funny sendup of the St. Crispin's Day speech from Henry V. And, while it’s not from a specific book, the image of the world being held up by elephants on the back of a turtle predates Diskworld by quite a long time.
The Diskworld novel about how a god’s power is proportional to the amount if belief it has is called “Small Gods”, which, coincidentally is the novel in the series the precedes this one.
I’ve always seen Granny as older than Nanny, but in a 70 vs. 50 kind of way. However, maybe that’s just me. Terry Pratchett has said that Nanny is the most powerful of the witches, but that she makes sure other people don’t find this out.
You mentioned how a novel centered on older characters is rare in fantasy, which is true. However, even rarer is that all the major battles in this book are between women. The men are secondary.
Diamanda rants about Granny changing the rules, but they were always playing by different rules. And, while Nanny is better at it, Granny is pretty darn good at manipulating people. She calls this “headology”.
Re the discussion of the early rising manager, I’ve worked in technology since the 80s and no one ever cared what time I came in. However, they for damn sure noticed when people left work. The net effect was that work started pretty late up into the early aughts.
Finally, a thing that I adore about Terry Pratchett is that he trusted his readers. He didn’t over explain, he just put the work out there and assumed we could figure it out. That’s part of why the jokes work so well and why he would write a “how magic works” section that’s separated by 14 pages.