Pratchett seems to have tackled a whole barrel load of big questions here: what makes societies work, the nature of belief, the nature of 'civilisation', the unfortunate tendency of people wearing rather more clothes to conquer people wearing less. In the hands of most other authors, it would probably seem like too much.
Pratchett handles it all with his customary skill and hilarity. Taking a simple story about a young woman (Daphne) shipwrecked on an island with a young man (Mau) and an increasing number of people left homeless by the tidal wave that wiped out the island's population, he weaves in uncouth parrots, grandfather spirits whose main concern is getting their beer on time, and a plot about finding the heir to the throne just in time thanks to the version of Magna Carta they don't show the public. It's utterly ludicrous and tremendous fun at the same time.
A Terry Pratchett book, in other words.