Tomorrow, When the War Began (Tomorrow Series #1)

When Ellie and six of her friends return home from a camping trip deep in the bush, they find that their country has been invaded and everyone in town has been taken prisoner. Life-and-death decisions must be made as they struggle with how to survive. "A riveting adventure through which Marsden explores the capacity for evil and the necessity of working together to oppose it." -- Horn Book, starred review