It wasn't a country or a city; it was barely even a town. But Nation was Mau's island home, and when a tidal wave destroys it and everyone he knows, his whole life is set adrift. The ghosts of his ancestors demand he return things to the way they used to be, but Mau is starting to question ghosts and gods on general principle. He isn't the only one on Nation; a ship from the land of the "trousermen" crashed on the island during the wave, leaving a foul-mouthed parrot and Daphne, a young woman whose father is 138th in line for the British throne. Together, Mau and Daphne have to survive, find purpose in their lives, and protect the other wave survivors who land on Nation. Meanwhile, the ghosts keep calling, and the island's secrets wait to be discovered.
Terry Pratchett is a funny man, no question. His Discworld books, a series of gentle (and sometimes not-so-gentle) fantasy parodies, teem with puns, banter, wit, and even the occasional joke. Nation is largely straight-faced, but it does have Pratchett's other two great strengths as a writer: his knack for storytelling, and his humanism. That humanism in particular stands out—as Mau and Daphne struggle to define themselves, their perspectives are described in the sympathetic, warm tones of an author who's seen far enough to know that the further out you go, the closer you are to coming home.
As far as plotting goes, Nation's main thread is strong, although some of the more esoteric elements aren't as effective. Pratchett makes points about the nature of gods and the wonders of science, but they fade in comparison to the main characters' grounded, day-to-day efforts just to get by. Many of Nation's conflicts will be familiar to his fans; the antagonist's particular brand of psychosis has often plagued Pratchett's work. But the familiarity seems less like a lack of imagination than like an acknowledgement that some evils can't be resolved. Pratchett doesn't fulfill all his ambitions, but his failures don't detract much from his successes. Nation is a young-adult novel that tries to teach children how to be adults; at worst, it's a solid adventure story, and at best, it asks hard questions and demands its readers show their work.