There's nothing wrong with this book. It's not bad at all. It's just that it's not particularly exciting or captivating. At no point did I feel like I couldn't put the book down yet because I had to see what happened in the next chapter.
That's probably because nothing really happens in this book.
The set up is really good. After the first couple of chapters, I thought I'd be in for an interesting story. The main character, Mau, lives on an island nation and belongs to a culture with all sorts of interesting traditions. He's about to make the transition from boyhood to manhood. Meanwhile, the majority of the British royal family has been killed by a plague and the man who is next in line for the throne is sailing in the same region as Mau's island. So is his daughter who was sailing to meet him. Then there's a giant storm which wipes out all of Mau's people and crashes the heir's daughter's ship on Mau's island (killing all other humans on that ship).
So, Mau meets up with the daughter and slowly builds a new nation on that island with other people who start randomly showing up. Pratchett deals with all the things that would realistically have needed to be dealt with - language barrier being the biggest. But I feel like there should have been a bigger "clash of cultures" and like there really ought to have been more plot than there was.