A Pratchett book for Christmas! Excellent!
Terry Pratchett writes two flavors of books these days: Pretty straightforward plot-driven books, and Message books. This is not to say that Message books don't have fairly rollicking plots, or that the Plot books don't have the Message, but that some are stronger in one than the other. This one's interesting in that it does character development for some people who have been around for numerous books, and that it takes them in slightly unexpected directions.
Ponder Stibbons— the only "sensible" member of the Unseen University staff— is busier than ever, but has managed to turn his intelligence towards something to make his life easier, i.e. understanding how to work Archchancellor Ridcully around. Ridcully, in turn, is still bluff and blustery but displays more of the intelligence that we've seen mere hints of before. Lord Vetinari, the Patrician, is as Machivellian as ever but displays a certain amount of human emotion other than annoyance or mild pleasure.
As far as plot goes, it's actually a comparatively minor event in Discworld terms. No end-of-the-world staff, no Dungeon Dimension Demons, no occult races making things difficult— just football (soccer, to us.) Okay, well, there's a god of football, but she makes almost no appearance, unusual in Chekhovian terms. And as far as message, it's the usual Pratchett commentary that people are individuals, but not presented very strongly. (Some books do bludgeon you over the head with it.)
Was it good? Of course. Was it stellar? Well, not in terms of his overall body of work, but quite serviceable for all that. A lot of people may find it a disappointment if they're looking for Sturm und Drang. But it's quite likeable, and if you approach it as an exploration into characters in a less frenetic setting, you should enjoy it just fine.