Magoo, my kids read Fleur Beale when they were at the local school. i used to read the books they brought home (being an avid reader and always looking for new stuff to read lol) so I have read most of the stuff she wrote for young teens. It was damn good reading
The local school got David Hill in to speak to the kids, which I attended. He also wrote some awesome young adult books, most of which I've read as well
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But my favourite young adult author would have to be John Marsden (I know he's Australian but he's really great - he wrote the "Tomorrow, when the war began" series).