I have noticed a repeated trend in the British psyche lately trying to recognize the fact that there were an empire for several hundred years. On the one hand, they want to take pride in the fact that they were once a mighty nation, on the other hand, they've grown up and realized that stomping people for economic exploitation is probably not the most morally superior attitude in the world.
Nation is a departure from Pratchet's work in many ways. It is set in the real world, despite hints and shadows at potential supernatural activity that might only be in the minds of the local participants. It answers important questions about culture, nationality, history and the individual. His characters are interesting; the female Daphne and the male Mau. He starts the narrative off with Mau because Mau is the most foreign to most of those who will be reading the book. Mau is a pacific islander (despite a handwavium attempt by the author to pretend that the island and the entire ocean have been made up out of thin air at the end of the book) while Daphne is the unlikely heir to the british empire after a plague killed dozens of other relatives, who ends up shipwrecked on the Island with Mau.
What is fascinating is how the two interact and how the question of the ultimate fate of the island is resolved in the long term. For young adult fiction (or fiction in general) it is quite good and I would highly recommend reading it. Most impressive of all, is that on top of the questions it asks and answers, Pratchet manages to keep his trademark humor throughout.