Almost since the day of his untimely death, Lou Gehrig has been invoked as one of a handful of baseball’s authentic heroes. When blustery Yankees owner George Steinbrenner boasts about his club’s “class” – even though he’s employed any number of personally disreputable athletes – fans recall the dignity of Gehrig, the “Iron Horse,” whose consecutive game record was broken by Cal Ripken Jr. in 1995. They remember the way he carried and conducted himself, especially while dying of the neuromuscular disease that now bears his name.

This impulse is understandable, especially in the past decade, when the steroids scandal, the players’ strike that cancelled the 1994 World Series, and exorbitant salaries have jaded the public’s view of the sport and the men who play it. There is a difference, however, between character and heroism.

Jackie Robinson, who broke baseball’s color barrier despite death threats and the constant racist bleats at stadiums, is undoubtedly the game’s foremost hero. And Gehrig, as Jonathan Eig points out in his fine biography, “Luckiest Man” (Simon & Schuster, 420 pages, $26), was a complicated man who certainly wouldn’t have the same folklore built around him had he not died at 38.

There’s no myth-shattering material in “Luckiest Man,” of the sort in books such as Richard Ben Cramer’s biography of Joe DiMaggio. Mr. Eig doesn’t presume to speculate what Gehrig’s ultimate legacy might have been had his life and career not been shortened.

But it’s clear from his exhaustively researched book – which includes interviews of Gehrig’s contemporaries, newspaper articles from the 1920s and 1930s, and the memoirs of his wife, Eleanor, and doctors who treated him at the Mayo Clinic – that the reserved slugger would not today be revered as a baseball saint.

Gehrig was born in 1903 to poor German immigrants and grew up in New York City, slavishly devoted to his overbearing mother who, having lost three other children to premature death, doted over her lone remaining son. Christina Gehrig tolerated her husband, Heinrich, who flitted from job to job and spent too much time in saloons. She concentrated her hopes on Lou.

Christina was at first aghast that a Columbia student would choose a career in baseball rather than law or medicine. As Gehrig became a star, however, she reveled in his on-field and financial success, even as she destroyed most of her son’s few romantic adventures. Gehrig finally married Eleanor – far more sophisticated and wily than her husband – when he was 30. Christina never forgave her daughter-in-law for stealing her son.

Mr. Eig is properly respectful of Gehrig’s extraordinary baseball achievements, but he deviates from the standard biography of the exalted first baseman – most notably captured in Gary Cooper’s 1942 portrayal of him in “The Pride of the Yankees” – by noting, repeatedly, the flaws of the beloved icon.

Gehrig was a notorious skinflint. Even after he’d achieved wealth, he tipped badly and left bills for others to pay. He didn’t carry cash with him, and he seemed oblivious to the contradiction of being a “rags-to-riches” man not particularly sympathetic to those with less money than himself.

This was a stark contrast to Babe Ruth, a larger-than-life personality who also came from humble circumstances. Ruth was not the most upright citizen, but he was exceedingly generous with the money he made playing baseball and endorsing commercial products. Gehrig privately resented the lavish attention given to Ruth – though he deferred to him in public – and wasn’t comfortable with his teammate’s dissolute habits.

Gehrig was also stubborn, vain, moody, and insecure, concerned about his consecutive-game record even when he knew the Yankees would be better off if he took more time off. He was respected by his teammates but had few friends, perhaps because of his strict allegiance to the Yankee management in an era when the owners held vastly more control over players than today.

Gehrig could also be downright mean. Mr. Eig interviewed Billy Rogell, a shortstop who Gehrig bowled over at second base during a game in 1934 – an injury that required stitches, even though it wasn’t a crucial play in the contest. Rogell, 97 when Mr. Eig spoke to him, was still “clearly upset” about an incident that occurred more than half a century previously.

Had Gehrig not succumbed to a still-fatal malady in the prime of life, he’d be remembered today by historians and fans alike as a great ballplayer, in the same company with fellow Hall of Famers like Rogers Hornsby, Hank Greenberg, Bob Feller, and Willie Mays. He was disciplined, worked hard, rarely indulged in the vices that shortened other players’ careers, and – most notably – was ahead of his time on the subject of racism in baseball.

Gehrig said in the 1920s, years before Robinson and civil-rights marches, “There is no room in baseball for discrimination. It is our national pastime and a game for all.” Considering the bigotry rampant among players at that time, only a star of Gehrig’s caliber could speak his mind so freely on such a topic.

Despite all this, Gehrig will always be associated with the stirring speech he gave on July 4, 1939 at Yankee Stadium, a few paragraphs that Mr. Eig describes as “one of the saddest and strongest messages an American audience had ever heard.” The dying ballplayer, who struggled to the microphone in front of a sold-out stadium, said at the outset, “Today I consider myself the luckiest man on the face of the earth.”

More than 60 years later, that’s still considered the “sound bite” of the occasion. But it’s what Gehrig mentioned after that, acknowledging the vast array of gifts given him, that demonstrates his courage and character, if not godlike heroism. He continued: “When the New York Giants, a team you would give your right arm to beat, and vice versa, sends you a gift – that’s something. When the groundskeepers and office staff and writers and old timers and players and concessionaries all remember you with trophies – that’s something.”

This is the “class” Mr. Steinbrenner crudely tries to draw from in describing his current Yankee team. And while it doesn’t place Gehrig in the same category as Jackie Robinson, it certainly sets him apart from his peers and modern-day athletes.

Mr. Smith last wrote in these pages on CBS News.