This was a terrific book - a futuristic view of our civilization a hundred years from now, when the polar icecaps have melted and the world is flooded. There are still islands with people living on them on former mountaintops. Mara is living on an island she knows as Wing. It took me a while to figure out that Wing is all that is left of Scotland. Her village is about to be swallowed by the rising sea and Mara, after researching on her handheld computer, has devised a plan to save the villagers by traveling by fishing boats to a "sky city" built above the ocean to withstand the storms that lash the earth. But the sky city of New Mungo is a closed society to refugees. So Mara must find a way in, and find a way to rescue the refugees she meets there. The futuristic New Mungo society is interesting, as are the different bands of refugees. All are believable, as is the dilemma posed by how to deal with refugees when to take them in means to overwhelm the available resources.
