Well I'm not sure what genre you're looking at but I think I'm supposed to recommend Tim Winton of the current authors.
There's also Di Morrissey, Thomas Kennealy, Peter Carey
Most of the Aussie books and authors that I love are semi autobiographical or not fiction so I'm not sure I can help much. In terms of great reads and great Aussie books my personal favorites include
Miles Franklin ~ My Brilliant Career
A.B Facey ~ A Fortunate Life
Joan Lindsay ~ Picnic At Hanging Rock
Anais (Jeannie) Gunn ~ We of The Never Never
Gregory David Roberts ~ Shantaram
Gabrielle Carey & Kathy Lette ~ Puberty Blues
Mandy Sawyer ~ Dreamtime Alice
Marie Mahood ~ Icing on The Damper
Garry Disher ~ The Divine Wind
Alan Marshall ~ I Can Jump Puddles
There's others but I can't think of them all right now, but they'll do for starters, hopefully.