When she came back crying, Gandhi "cackled" and purportedly said: "If some ruffian had carried you off and you had met your death courageously, my heart would have danced with joy," according to the book.
The author also alleges that Gandhi had racist attitudes when exposed to "kaffir," as blacks were called in South Africa.
As early as 1894, he wrote a letter to the Natal legislature, "the raw Kaffir, whose occupation is hunting and whose sole ambition is to collect a number of cattle to buy a wife, and then pass his life in indolence and nakedness."
"We were marched off to a prison intended for Kaffirs," he is alleged to have said. "We could understand not being classed with whites, but to be placed on the same level as the Natives seemed too much to put up with. Kaffirs are as a rule uncivilized."
Some Indian scholars said Gandhi may have even viewed blacks as "untouchables," the lowest class in his homeland.
As for Gandhi's racial attitudes, they too, are inconsequential when seen through the lens of the Indian leader's larger political struggle, according to scholar Chakrabarty, who has authored three books on Gandhi.
"He was a smart and strategic politician," he said. "He was more concerned about removing racism against England. It's true, he didn't pick up the black issues in South Africa, but that was not his fight."
"He didn't want to dilute his political ambition," said Chakrabarty.
The Wall Street Journal review of the book said it recast Gandhi as "a sexual weirdo, a political incompetent, a fanatical faddist, implacably racist, and a ceaseless self-promoter, professing his love for mankind as a concept while actually despising people as individuals."
Lelyveld says in his author's note that the book takes "a fresh look, in an attempt to understand his life as he lived it. I'm more excited by the man himself, the long arc of his strenuous life, than by anything that can be distilled as doctrine."
At the age of 13 Gandhi had been married to 14-year-old Kasturbai Makhanji, but after four children together they broke up so he could be with Kallenbach.
As late as 1933 Gandhi wrote a letter telling of his unending desire and branding his ex-wife "the most venomous woman I have met."
Kallenabach emigrated from East Prussia to South Africa where he first met Gandhi. The author describes Gandhi's relationship with the man as, "the most intimate, also ambiguous relationship of [Gandhi's] lifetime."
"They were a couple," said Tridip Suhrud, a Gandhi scholar who met Lelyveld in India.
The source of much of the detail of their affair was found in the "loving and charming love notes" that Gandhi wrote to Kallenbach, whose family saved them after the architect's death. They eventually landed in the National Archives of India.
Gandhi had destroyed all those from Kallenbach.
It was known that Gandhi was preoccupied with physiology, and even though he had a "taut torso," weighing 106 to 118 pounds throughout his life, the author says Gandhi was attracted to Kallenbach's strongman build.
The pair lived together for two years in a house Kallenbach built in South Africa and pledged to give one another "more love, and yet more love."
Gandhi implored Kallenbach not to "look lustfully upon any woman" and cautioned, "I cannot imagine a thing as ugly as the intercourse of men and women."
By the time Gandhi left South Africa in 1914, Kallenbach was not allowed to accompany him because of World War I. But Gandhi told him, "You will always be you and you alone to me...I have told you you will have to desert me and not I you."
Kallenbach died in 1945 and Gandhi died in 1948.