Autobiographies, particularly autobiographies of famous people take several different forms. Normally there's a ghostwriter involved, and the celebrity may not have very much involvement in the book. Most famously, Charles Barkley claimed to have been misquoted in his autobiography. Sometimes the celebrity is very involved and actually even writes, or at least sets the tone of, much of the book.
Having never met or had personal contact with Mike Leach, it's difficult to say how precisely Swing Your Sword: Leading the Charge in Football and Life matches his personality and personal style. That said, I've read a decent amount of Leach-related material the last few years, and Swing sounded an awful lot like what I think Leach looks like. Some credit for this must go to his ghostwriter, Bruce Feldman, but Swing is a very engagingly and entertainingly written tour of Mike Leach's life up to and through his termination by Texas Tech and his relocation to Key West.
Beyond the degree of involvement to the celebrity, one of the things that helps dictate how interesting a celebrity autobiography is is just how ... revealing the celebrity is interested in being. Swing is a tour of Mike Leach's life, starring Mike Leach and Mike Leach's career and accomplishments. He's worked and come into contact with some people who are interesting and/or accomplished, like Hal Mumme, Bob Stoops, and Dana Holgorsen, but even people who give half-page or one page blurbs, like Leach's quarterback at Texas Tech Graham Harrell, don't come alive. They're mostly paper cutouts, not fellow stars in the firmament.
That relative lack of depth is a recurring theme in the book. You get a feel for Leach and the way he thinks, but I'm not sure it's hugely deeper than what I already knew. Swing is probably best viewed as an entertaining trip through an entertaining coach's career.
For a much more useful review, see that by Chris Brown of Smart Football, who has had both personal contact with Leach and more familiarity with the airraid offense and Leach's version thereof.