Now a new book on Scottish independence by the polymath will address how Scots were also "settlers and colonists" in other countries.
Gray, who is also releasing his first autobiographical collection next month, called Of Me & Others, revealed details of his other new work, which will be published by Canongate in June.
Last year Gray, known for his paintings as well has his authorship of books such as Lanark and what he calls his "best novel", 1982 Janine, caused controversy with an essay that concerned English "colonists and settlers" in Scotland.
He said of the book, which he is still writing: "I am revisiting that, very strongly, I was quite astonished by the stir it caused. One of my chapters is dealing with what settlers and colonists the Scots have been in other countries - I am making that a major chapter, I am not taking the position of 'we are holier than you English'.
"Both Scotland and Ireland have been major exporters of people."
Another chapter in his independence book is on "the fear project": what the writer considers to be attempts to scare Scottish voters into voting against independence.
"I think the 'big bogey man approach' is becoming so blatant," he said.
Of the independence referendum, he said: "I am optimistic. I don't have much faith in opinion polls. I certainly will not feel suicidal if the thing is lost, but whether it is won or lost it will be by a narrow majority, but the country will not go away."
Of Me & Others, to be published on April 12 by Glasgow book company Cargo, contains writing on friends and influences, including RD Laing, Tom Leonard, Liz Lochhead, Archie Hind, the publisher Bill MacLellan, Susan Boyd, and Anthony Burgess, as well as prologues and epilogues to existing works.
"It's not a planned autobiography, it's more of a collection of prose essays written between the ages of 17 and last year, when I was 78," he said. "Some of them are personal reminiscences, some of them are articles I wrote at the time, some are introductions to earlier books I wrote, and some, alas, are obituaries for people I have known."
He added: "I do not go into details about my private love life, which I may say was not a very big one. I was not in any way a Casanova.
"The first woman I slept with I married, and my present and certainly last wife (Morag) I met in 1999, we married in 2001 and have been together ever since - so I don't go into details about that, it is about work and friends.
"I would not say it is about 'my career', that makes it sound like a mad and exciting forward charge."
Gray said his grand-daughter, Alexandra, the daughter of his son Andrew, was also studying visual art in America where she grew up, and would shortly come to Scotland for an internship.
"I am really looking forward to it, I have seen her early work and it is inventive and funny, she has a sense of humour," he said.
Of Me & Others is to be launched at the Aye Write! Book Festival. The Herald is media partner.