Aram Goudsouzian’s books include “King of the Court: Bill Russell and the Basketball Revolution” and the forthcoming “The Men and the Moment: The Election of 1968 and the Rise of Partisan Politics in America.”

The mob swarmed around Babe Ruth. In the ninth inning of an exhibition game at Brooklyn’s Dexter Park, just days after the New York Yankees’ triumph in the 1927 World Series, masses of unruly fans were trampling over the field and each other, shoving backs and swinging fists, packing ever closer to the Sultan of Swat. According to one account, a phalanx of policemen had to guide him to safety.

Ruth was grinning. He loved it.

In the 1920s, Babe Ruth was a new kind of public man, a personification of modern America. He not only reinvented baseball with mighty uppercut swings, ushering in the age of home runs. He also relentlessly insisted on living on his own terms: getting paid as he deserved, consuming as he pleased, crafting his own image, reveling in celebrity. In her engaging biography “The Big Fella,” Jane Leavy writes that Ruth “exploded notions of the doable.”

As with her celebrated books on Sandy Koufax and Mickey Mantle, Leavy eschews a traditional birth-to-death structure. “The Big Fella” revolves around a three-week cross-country barnstorming tour after the World Series in October 1927, featuring Ruth in his black “Bustin’ Babes” uniform with a white cap and Lou Gehrig in his white “Larrupin’ Lous” costume with a black hat. The tour provides a setting for Ruth at the height of his power, and it illustrates his hold on people — 13 of the 21 games, including the one in Dexter Park, finished prematurely because of his fans’ excessive ardor.

“The Big Fella” omits many of Ruth’s feats as a ballplayer, but previous biographies have trod all over that ground. Instead, Leavy shines light on Ruth’s place in American cultural history. She paints a sensitive and humorous portrait of a flamboyant figure who exploited technological transformations, public appetites and his athletic prowess to forge a new sporting celebrity.

His love for attention derived from his harsh childhood. Leavy sifts through the myths of the young Babe, painting a colorfully seedy picture of turn-of-the-century Baltimore. Four of Ruth’s siblings died at young ages. His father filed for divorce from his philandering mother. He lived above a saloon and caused mischief on the streets. When he was 7, his father sent him to a boarding school for orphans and incorrigibles. “Parental abandonment would become the defining and unacknowledged biographical fact of his life,” writes Leavy. “It is the lens that clarifies; the mystery he would never explain.”

At St. Mary’s Industrial School for boys, he had no real private life — there were boys everywhere. His schedule was regimented, and his food was rationed. But he had caring mentors and a faculty for baseball. In 1914, he went straight from school into the ranks of professional baseball.

Instead of detailing Ruth’s early years with the Boston Red Sox or his 1919 trade to the Yankees, Leavy explains how Ruth became the first athlete whose fame transcended the playing field. He relied on Christy Walsh, an advertising pioneer and prototype agent. Walsh arranged the barnstorming tours, as well as Ruth’s turns in vaudeville, radio and movies. Ruth became one of the first celebrity pitchmen for consumer goods. Perhaps most important, he was the star in Walsh’s syndicate of newspaper columnists, which included Ty Cobb and Knute Rockne. This ghostwritten fluff got stuffed into sports pages around the country, shaping Ruth’s public persona. After a scandal — which often befell the big fella — it polished his image as necessary.

Ruth embodied excess. In the spring of 1925 he endured the “bellyache heard round the world,” a spate of boils, sweats and dyspepsia stimulated by his ballooning weight. That summer, the New York press fixated on his mistress Claire Hodgson, who would later become his second wife. Throughout his heyday, he accumulated speeding tickets and sexual partners. He indulged in 18-egg omelets and hot dogs by the dozen. He swilled fifths of gin mixed with quarts of fruit juice. In the Yankee clubhouse, at least, he never flushed the toilet.

But these prodigal ways inspired a new sports celebrity. In a Jazz Age milieu of flappers and gangsters, Ruth joyfully flouted convention. “He never embodied the traditional public virtues that defined ancient celebrity, and he didn’t have to,” writes Leavy. “Instead, he gave the public glimpses of a bad boy having the time of his life.” Ruth was no role model. He was an escape from the humdrum, a burst of fun.

That defiance of custom also shaped his revolutionary impact on baseball. Despite his tomato-can frame and toothpick legs, Ruth possessed extraordinary agility and power. He would have excelled at baseball in any case (he went 94-46 as a pitcher, mostly in his early career with the Red Sox). But prior to Ruth, a home run was a rarity. Unlike the predominating contact hitters, he swung upward, from his hips, creating the torque to launch 714 career home runs. Each of those homers, Leavy writes, “was the act of a man who defied expectation and authority at every turn.”

As she did with Koufax and Mantle, Leavy muses upon our tangled relationships with baseball heroes. Following the path of the 1927 barnstormers, she probes the memories of those who had fleeting moments with Ruth. She uncovers scraps of film that provide silent glimpses of the Bambino. In Kansas City, Ruth was photographed holding a baby in a black orphanage. It appeared only in black newspapers, reflecting racial segregation in baseball and the nation. African Americans often appreciated Ruth’s willingness to compete with Negro Leaguers. Yet the dark-skinned Ruth grew enraged at the rampant speculation about his origins — when he broke into baseball, his nickname was a racial epithet.

Ruth retired in 1935 after an aborted, desultory year with the Boston Braves. He never realized his desire to become a big league manager. In 1948 he succumbed to esophageal cancer. Though he remained a beloved and celebrated figure, Leavy dwells on an irony: Ruth had thrived by constructing himself as an impulsive man-child, but he never escaped that image. And without the fans’ roars, there was little left to smile about.

The Big Fella

Babe Ruth
and the World He Created

By Jane Leavy

Harper. 620 pp. $32.50