This isn't really a proper review, as I am stretched for time, and even moreso after wasting a few hours finishing this book. Though, of course, wasting is a misnomer here.

UU is an important addition to the Discworld Universe, and is well written, though it is not Pratchett at his best and has its flaws.

We are introduced to some new interesting species on Discworld, though I feel there are too many (at least 4 that I can recall, 1 only in passing). We see some more, from a distance, of Uberwald and Pseudopolis. The Wizards are entertaining and I can't help but like Stibbons and Ridcully far more after this book. Rincewind has an in character cameo. Dr Hicks/Hix becomes an ever more interesting character. The only character that seemed off initially was Vetinari: Pratchett seemed to struggle with the dialogue/monologue at the start of the book and the Patrician's speech suffers to begin with, but that improved later on, and we learn a bit more about Vetinari, which is good.
The new characters are well-constructed and developed, if stereotypical in some cases (see, Andy).

The usual allusions to other influences is, as always, clear enough to be visible but changed and subtle enough to make the story MORE original and entertaining. It occurs to me that Discworld is what the Epic/Scary etc. Movie series would be if it had any (well, a lot of) wit, writing skill or class.

We also see Ankh Morpork progress some more, which is interesting, and although some sections of the text are essentially info-dumps, on the whole they are well-written ones.

All in all, the plot is perfectly acceptable (better than the early plotless books, not as good as the City Watch, with a slightly better ending than the Moist books, where the plot is OK but the ending is always an anticlimax, IMO), the characterisation ends up being very good and the humour and references are understated but delicious as ever.

4 stars