I'd read this before in print form, but picked up the audiobook (read by Stephen Briggs, long time collaborator with Pratchett) and have to say the audio version was brilliantly done and gave real warmth and life to all the characters.

The book itself is a stand-alone, not part of the Discworld or any of Pratchett's other series; it's set on an alternate version of earth, I think somewhere around Victorian times (or the other-universe equivalent thereof). A massive tsunami hits a tiny archipelago of tropical islands including "The Nation", which is the island of the boy Mau, who is returning from his boyhood testing ceremony to become a man. Mau, being in a boat, survives; the rest of his island does not, so he arrives expecting to complete the ceremony to become a man and instead spends days retrieving and putting to rest the bodies of every single person he has ever known in his life so far.

At the same time, the British ship Sweet Judy is caught by the tsunami and swept into the archipelago, leaving young Daphne (aka Ermintrude) the sole survivor. She and Mau meet in the wreckage of his former home and slowly find ways to communicate and rebuild and deal with grief and strangeness.

It's a little hard to describe exactly what the book is about. It's about Daphne and Mau, learning to understand each others' different cultures and to reach across that gap for common ground. It's about learning to deal with loss and grief, and about hope. It's about valuing other cultures, and does strongly make the case that "primitive" cultures like Mau's are not in fact primitive at all; in fact I felt that Pratchett went a little far in the wish fulfillment direction here, as Mau's culture and how it's dealt with in the story are a rather starry-eyed alternate reality dream of how it MIGHT have been when colonial culture met a "primitive" tribe and actually behaved in a civilized way, instead of really any of the ways it actually happened in our own universe's history. And of course, being a Pratchett book, it's also about people, and how we are all people with all our flaws and strengths and foibles. And there's a lot of charming imaginary detail in there too about Mau's island and its unique ecosystem that includes pink bananas and the tree-climbing octopus among other things.

It's not a typical Pratchett book, and has fewer outright jokes and asides than a Discworld book, although there are still plenty of funny moments. But it is still a typical Pratchett book in that his view of humanity and all our various weaknesses and peculiarities comes through very strongly.