As post-apocalypse goes, this one's actually relatively possible. The Northern hemisphere has already destroyed itself with a vast nuclear war and, in the South of Australia, people have nothing really to do but sit and wait for the radiation to make its way south and kill them too.
I really really liked it. I liked how the characters know approximately when they're going to die for the entire book, something like three years in their time (I think). They start out doing things that you think you'd do if you knew when you were going to die (drinking a lot, sleeping around, lots of parties, quitting their jobs) but, after a while, they start to realize that the only way to survive until the end is to live as if there will be no end. They plant gardens and talk about the vegetables they'll have next year, when they'll never live to see another year. They go back to college, even though they'll never graduate. They have babies that will never grow up. It was really beautifully put together and the steadfast melancholy of it crept into my dreams last night.