By Manning Marable, Viking Penguin, New York, N.Y. 594 pages, $30

Before his assassination at age 39 in February 1965, Malcolm X was the most provocative human rights activist of his generation. In the years since his death, his legend has continued to grow, aided by a posthumous autobiography that has been read by millions, but which told only a part of his compelling story. Now, in the twilight of his own life, the late Manning Marable has produced a magisterial biography that fills in much but not all of the rest of the canvas.

The book is aptly named because Malcolm underwent many transformations. Born to a large family in the Midwest, his parents were followers of Marcus Garvey, who espoused racial pride and self-reliance. When Malcolm was 6, his father, an outspoken minister, was killed in a mysterious streetcar accident. By age 13, his mother, who had struggled to keep the family together, was institutionalized, leaving Malcolm to be raised in a series of foster homes, where the excellent student drifted into a life of crime.

In 1946, Malcolm was sentenced to a long prison term in Massachusetts. While in prison, he was mentored by an older inmate, John Elton Bembry, to read and educate himself, and was urged by his siblings to join the Nation of Islam (NOI), a black separatist and quasi-Islamic sect based in Chicago. Following his conversion, he discarded his surname (Little) and replaced it with an “X,” which symbolized the African family name that had been lost through slavery.

Upon his release from prison in 1952, Malcolm visited the NOI’s leader, Elijah Muhammad. He became an NOI minister in 1953 and, over the next decade, was instrumental in expanding the sect’s membership. An accomplished speaker and adroit courter of the media, he gained widespread recognition for his rhetoric and relentless disparagement of racial prejudice. By early 1964, however, he had broken ties with the NOI, converted to a Sunni Muslim, and espoused Pan-Africanism. It was during this final transformation that he was assassinated by three gunmen in 1965.

Although many books have been written about Malcolm X, Marable’s work stands out because of the quality of the scholarship and his access to sources that were previously unavailable to other authors. These sources included Malcolm’s own diaries, recordings of Malcolm’s speeches and other archival material from the NOI, a nine-hour interview with Louis Farrakhan (Malcolm’s mentee and successor as the NOI’s national minister), and countless interviews with Malcolm’s contemporaries.

One of the book’s most intriguing aspects is its deconstruction of “The Autobiography of Malcolm X,” a collaborative effort between Malcolm and Alex Haley that was published after the assassination.

Through painstaking research that produced a detailed chronological grid of Malcolm’s life, Marable and his research team, which he generously credits, conclude that although the “Autobiography” is a “brilliant literary work,” it is “more of a memoir than a factual and objective reconstruction of a man’s life.”

Marable also meticulously analyzes the different purposes that Malcolm and Haley brought to the “Autobiography.” For Malcolm, the book was supposed to present a “tale of moral uplift” and the explanation for “his break from black separatism.” For Haley, a liberal Republican and 20-year veteran of the U.S. Coast Guard, the book was a “cautionary tale about human waste and the tragedies produced by racial segregation.”

After Malcolm X left the NOI in early 1964, he made two trips to the Mideast and Africa, which profoundly changed his life. As recounted by Marable, as Malcolm traveled the world, he learned that “orthodox Islam was in many ways at odds with the racial stigmatization” of the NOI.

While the first of these trips, which included Malcolm’s pilgrimage to Mecca, is discussed in the “Autobiography,” the second trip, a four-month sojourn through Africa, is not. In richly detailed chapters, Marable chronicles this second trip, which began with the second meeting of the Organization for African Unity in Cairo, and proceeded through several new African nations, where Malcolm conferred at length with Kwame Nkrumah and other revolutionary leaders.

It was during this second trip that Malcom’s new organization, Muslim Mosque Inc. (MMI), was admitted to the Islamic Federation of the United States and Canada, and he was named to the federation’s board of directors.

According to Marable, these “two important stamps of legitimacy” positioned MMI for “Arab financial aid and, indirectly, political support to African Americans.”

Marable posits that these developments portended an isolation of the NOI, making it difficult for the NOI to assert new initiatives in, or send delegations to, the orthodox Muslim world. The author concludes that Malcolm’s success with and acceptance by the federation may have “sealed [his] fate among the NOI leaders.”

One of the book’s most controversial passages is its re-examination of the assassination, which took place at the Audubon Ballroom on the afternoon of Feb. 21, 1965.

Since his break from the NOI, Malcolm had been the target of death threats. Through Marable’s extensive analysis of “forensic probabilities, not certainties,” he concludes that, of the three NOI men who were later convicted for the murder in 1966, two were likely innocent of the crime. He also writes that the FBI and NYPD, both of which had informants present in the ballroom at the time of the shooting, probably had advance knowledge of it. Although this portion of the story is compelling and raises many disturbing questions, the answers are few. Thus, Marable had to leave the canvas unfinished.

A strength of the book is Marable’s insightful explanation of the reasons why Malcolm X is remembered today as an iconic figure. Audiences responded to his message because he spoke with uncommon “clarity, humor, and urgency” at a time when America had to overhaul its racial attitudes.

Marable observes that, even when he made “controversial statements with which a majority of blacks strongly disagreed, few questioned his sincerity and commitment.”

Through Marable’s narrative, the reader is able to envision the man who decried injustice, was impatient with phoniness, and was fearless about advocating change that was long overdue.

Jeffrey Winn is a partner with Sedgwick LLP.