Ferguson describes the day City won the title at United's expense as the worst of his life.
The Scot also has a dig at Mancini in the book, criticising his decision to keep Carlos Tevez on the books after the Argentinian refused to come off the bench in the club's Champions League game at Bayern Munich.
"Taking him back showed desperation," Ferguson writes.
"In terms of his prestige as a manager, he let himself down."
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