I've only started reading him. He does hard science fiction.

"Dichronauts" (2017) (finished) takes place in a universe with different laws of physics. The story itself isn't too complicated, but it is interesting. It basically shows us what life is like for a particular group of people.

"Permutation City" (1994) (halfway through) (which is Mature Audiences Only for one or two graphic sex scenes and a bit of graphic, catastrophic violence) takes place on a futuristic Earth with the main characters living in Australia (although that's incidental). It deals with much heavier themes of existence and consciousness.

If this list is for books that are not merely by Australian authors, but also recognizably take place in Australia, Perihelion Summer would be a better choice than Permutation City. Perm. City only nominally takes place in Australia, sometimes. Peri. Summer is more firmly rooted in Australia and environs.

As for what it's about, well, if you like disaster movies, you'll like Perihelion Summer.