His first serious novel, published when he had left Australia and settled in London, was a World War II story, Instruments of Death (1973; entitled None But the Damned in the US).

This was followed by an avant-garde novel, Knock (1975), described in the foreword by Colin Wilson as a work that "belongs to an Irish tradition that runs from Charles Lever and Samuel Lover, down through Joyce, Beckett and Donleavy".

The book claims to provide conclusive proof that flying saucers are made in Antarctica using Nazi technology and a slave colony of ex-concentration camp inmates.

In 2005, Harbinson self-published his autobiography, The Writing Game: Recollections of an Occasional Bestselling Author, as a POD book, later as a Kindle e-book, released through Amazon's CreateSpace.

Harbinson's early Australian novel The Running Man was turned into a feature film entitled The City's Edge.