'Unseen Academicals' is an excellent book. It's also exactly the right book to read during the 2010 World Cup. It's also a triumph of Pratchett being Pratchett at his best.
But it's also unlike any of his books before this, because there's not going to be an infinite number of them in the future. Pratchett thanks the person who typed this, at the beginning. Because he can't type his own books any more. He knows that whatever he still has up his sleeve and wants to say, he needs to get it out soon before the Alzheimer's gets at it all. So there is a plethora of new things we haven't seen before in Discworld:
- A simply, unequivocally, unmetaphorically gay character. He's a bit of a pompous twat as all wizards are, he's a phenomenally good footballer, and he's had to flee from Genua because of some scandal with a bloke. Then, Ponder and Ridcully blather around a little in embarrassment, then something else happens, end of tale.
- Orcs. The dilemma of the orcs is something very basic in Tolkien and all the high fantasy that uses them. Orcs were created by the Dark Lord (Morgoth, in the original passage in the Silmarillion) out of innocent people (elves) that were captured and tortured until they did his bidding. Basically, he made himself an army out of nutcases with dreadful PTSD. They do make effective killers (see Urquhart and the others from that mold that populate the books of his author), but why is it that among all creatures of Middlearth and suchlike worlds, orcs are unredeemable and can be killed by the hundred for the sake of competition. They were victims, originally, for krissakes!! Pratchett picks up that ball and runs with it as gloriously as anybody ever did.
- A generational change. Ponder Stibbons is really running UU now, by means of having accumulated so many chores that nobody else wants, he basically only reports to himself. He has matured a lot and may be the only sane wizard ever. And Vetinari isn't totally in control throughout any longer, either. The game has a serious chance of turning against him. And at the very end, Glenda and Nutt really show up Margolotta and Vetinari. Between them, they're the most powerful people on the entire Disc, and they have to cede a draw (at the least) to a pie baker and a football coach.
- Lack of cynical turnarounds and stupid misunderstandings. No, the passengers to Sto Lat do not turn against Nutt at a later stage. No, Bengo Macarona's sexual orientation is neither a misunderstanding, nor does anybody go on and on about what they thought it meant. There is genuine shiny. The candles Nutt makes. Juliet's prettiness, and the efficacy of micromail. The goal Macarona scores. The favour Glenda does for the old ladies in her neighbourhood.
- Public transport. Ankh-Morpork has acquired a system of horse buses and 'trolleys' (= trolls carrying panniers in which people can ride), and there is a night bus to Sto Lat.
- Überwaldean philosophy. We knew there was some sort of learning, but only Nutt quoting an endless number of works shows us that we may assume that anything ever theorised about in the last two centuries in our actual Roundworld, from Hegel and Nietzsche via Freud and Wittgenstein to Fukuyama or Taleb, has been in some way thought and written about in Überwald. That is something that we the fans can take and run with.