While Aldridge has claimed that it is "no surprise" that the Scotsman has been critical of arch rivals Liverpool in the book, the 55-year-old is baffled by his words regarding the England skipper.
"It was no surprise to see Fergie stick the boot into Liverpool, he's done that for the last 30 years or so, but he's barking up the wrong tree when it comes to Steven Gerrard," Aldridge told the Liverpool Echo. "I guess it's just a way to ensure he sells more copies of his book.
"Any manager or player who has ever come across Steven in the game will tell you he's world class. Steve has never had the team around him to win a league title, but a look at his career tells you that he is a world class footballer, and he's had some great games against United down the years. How Ferguson can be critical of the lad, well, words fail me.
"We all know what Sir Alex thinks of Liverpool, he's on record enough times telling us, but I think the fact he admits he would have signed Steven Gerrard tells you exactly what he really thought of the player."
Ferguson also wrote that it is "absolute nonsense" to claim that Gerrard is a better player than ex-United midfielder Paul Scholes.