The secrecy, and sale, was due to the public tempest following the writer's financial woes.
After a troubled childhood, he shot to fame and considerable fortune with Once Were Warriors, before making a hasty descent on the back of a much-publicised bankruptcy. His was a zero-to-hero-to-zero saga.
There are few in his former province who don't hold strong opinions of the talented scribe.
But part of his legacy that's seldom spoken of is the Duffy Books in Homes programme. Until then, the privileged, like me, were not aware there was any other sort of home.
Camberley School this month celebrates the 20th anniversary of the programme, which was founded and inspired by the author's visit to the school.
While I suspect Mr Duff may have written his finest novel, this lesser mentioned triumph - 9 million books gifted so far - must be considered his bestseller.