The pacing of the book was excellent, but I felt the characters were a little wooden. This especially comes out in the dialogue; everyone sounds the same. Also, each of the survivors are kids - and I never got the sense that these children were forced to grow up too quickly.
Characterization aside, it was really neat reading about Australia. Obviously, it's not a tour guide, but the little nuances of speech and culture were fascinating to me. The action was what really makes this book; Ian has a superior grasp of pacing and the way the civilization rumbled to a halt was plausible, as were the survivor's reactions.
There's a mention at the end of the book of a sequel, and I expect I'll read it. Not so much because I'm interested in Karen as much as I am the post-apocalyptic world that Ian created.
This was a very, very quick read - I banged it out in one sitting. It's worth the couple bucks he's charging for it at smashwords.