He was awarded the A.O. (Officer of the Order of Australia) in the 1995 Queen's New Years Honours List for his services to Literature.
His surname is pronounced "Kosh".
His father was an accountant. His mother had attended high school on Tasmania with Errol Flynn.
He worked in the art department of a newspaper, before graduating from the University of Tasmania in 1954. He published his first novel in 1958. He subsequently attended Stanford University, where he studied writing; his fellow students included American writers Ken Kesey and Larry McMurtry.