This week, Unshelved recommends Tomorrow #1: When The War Began by John Marsden:
Here is a review of the book from Amazon.com:
When Ellie and her friends go camping, they have no idea they’re leaving their old lives behind forever. Despite a less-than-tragic food shortage and a secret crush or two, everything goes as planned. But a week later, they return home to find their houses empty and their pets starving. Something has gone wrong–horribly wrong. Before long, they realize the country has been invaded, and the entire town has been captured–including their families and all their friends. Ellie and the other survivors face an impossible decision: They can flee for the mountains or surrender. Or they can fight.
This is the first book of a series, so if you enjoy it, there are several others to keep you entertained.