Jonathan Eig is the Pulitzer-Prize-winning author of “King: A Life.”

Having placed Muhammad Ali in the canon of civil rights leaders with his 2017 biography, Eig turns to Martin Luther King Jr. (1929-1968) in a monumental biography.

King did not begin life with that name: His parents “named him Michael King, no middle name, no initial, no ‘Junior.’ They called him Little Mike.” Though small, he was a scrapper on the football field and basketball court, a smart and serious student who entered Morehouse College early and, having traveled north on a work program and seen the magic of desegregation, became committed to civil rights.

The name change, writes the author, “was clinched during a 1934 trip to Germany, where King learned more about the 16th-century German friar.” King first forged the battle for civil rights in Montgomery, Alabama, in 1955; in the 13 years he had left, he galvanized that struggle, carefully planning campaigns while refining his skills by, among other things, visiting India to study the nonviolent tactics of Gandhi.

Although King “was a man, not a saint, not a symbol,” he was viewed both positively and negatively as the most important advocate of Black rights — a program he would expand to include an anti–Vietnam War platform and a widening effort to end poverty worldwide.

That spread him thin, but not enough to elude the obsessive hatred of J. Edgar Hoover, who “saw King as the ultimate disrupter of societal norms.” That he was, even if he was seen as too conservative by some Black militants and too radical by many Whites.

Unlike biographers hitherto denied access, Eig examined recently released FBI files to show that there is no evidence that King was a secret agent, as Hoover alleged, though the files do show “the extent and determination of the bureau’s campaign to thwart King.”

This book recounts the extraordinary life and achievements of an iconic warrior for social justice.

Eig is the author of six books, four of them New York Times best sellers. His works have been translated into more than 20 languages.