"The Night is for Hunting (The Tomorrow Series #6)" by John Marsden
https://www.amazon.com/gp/product/0439858038/

Book number six of a seven book young adult action adventure fiction
series. I read the well printed and well bound trade paperback
published by Scholastic Paperbacks in 2007 that I bought on Amazon. The
first book in the series was actually published in 1993, this book was
first published in 1998. Book #6 is out of print so I had to order a
used copy. I have also bought book #7 from Big River. And of course I
found out that I could have bought the entire series in trade paperback
at a discount:
https://www.amazon.com/gp/product/B00IWWCXBC/

At the middle of their high school senior year in Australia, a group of
seven 17 and 18 year old teenagers decide to go camping in the bush for
a week before school restarts. They gather up their sleeping bags and
supplies and go way out into the bush, actually at the edge of the
desert in a place known as Hell. After a difficult trip by Land Rover
and a long walk, they camp next to a spring fed stream. When they
return to Ellie's farm after a week, her family is missing and the farm
dogs are dead on their chains. They find out that Australia has been
invaded by an Asian nation and that their families are being held
captive at the town fairgrounds. The Asian forces have taken the
airports first and then the cargo shipping seaports. The justification
of the invasion is that the Asian nation needs the extensive natural
resources of Australia.

It has now been a year since the invasion began. Ellie and her
remaining friends blew up the huge airbase in the region by sneaking in
the back of a supply truck and throwing grenades into the jet fighters
being refueled. They managed to escape in the confusion by jumping in
the river and floating twenty miles to the next town. While laying low,
they rescued several orphan children. Now what do they do ?

The first book in the series was made into a film of the same name in 2010.
https://en.wikipedia.org/wiki/Tomorrow,_When_the_War_Began_(film)

My rating: 4.5 out of 5 stars
Amazon rating: 4.6 out of 5 stars (94 reviews)

Lynn