The revealing book, which contains details about Keane's shock sacking by Manchester United, and a drink-fuelled fight with Peter Schmeichel, was due to go on sale on Thursday.
But publishers Weidenfeld & Nicolson was left stunned when a Tesco store in Burnage, Manchester, put copies of The Second Half on its shelves on Monday morning.
A big publicity launch has been scheduled for the original release day in Dublin, but contents of the book have already been published online.
"A copy of Roy Keane's book was sold in error at our Burnage store," a Tesco statement read.
"Colleagues are currently investigating how this happened."
The supermarket removed the books from its shelves shortly after realising it had made an error.
The former Republic of Ireland midfielder, now assistant manager at Aston Villa, hit the headlines for writing about the tackle that ended Alf-Inge Haaland's career in his first book, which was published 12 years ago.
And his latest autobiography appears to be just as revealing, with details about his departure from United among a series of fascinating tales from the 43-year-old former Nottingham Forest player.
Source : PA
Source: PA