Alex Haley was a working freelance writer, not an ideologue. Yet he wrote two of the 20th century’s chief texts of African-American consciousness: “The Autobiography of Malcolm X” and the saga “Roots.” The latter was adapted for a blockbuster TV miniseries watched by a reported 130 million viewers.

In “Alex Haley and the Books That Changed a Nation,” Robert J. Norrell describes the making, often messy, of these seminal books and their powerful impact on American culture. He also grapples with questions about them, including the criticism that Haley softened Malcolm’s point of view on black nationalism, and accusations that Haley plagiarized parts of “Roots.”

Norrell is a professor of history at the University of Tennessee and author of “Up from History: The Life of Booker T. Washington,” a biography that Jonathan Yardley praised for making him rethink his take on Washington.

Born in small-town Tennessee, Haley (1921-1992) joined the Coast Guard in 1939 as a “mess boy” and later cook. He had liked writing but hadn’t envisioned it as a possible career. On ship, he wrote romances to submit to confessional magazines. Soon enough, for $1 each, he was writing love letters on behalf of fellow crewmen.

Later, he worked in Coast Guard public relations while pitching freelance stories to national magazines. In San Francisco, the popular writer Barnaby Conrad (“Matador”) became a mentor who coached Haley while also introducing him to other writers and celebrities.

As Haley struggled to establish himself as a writer, particularly after his retirement from the Coast Guard in 1959, he concentrated on autobiographical approaches and stories of black achievement. Norrell notes that Haley made a regular connection with Reader’s Digest – which led to Haley interviewing Malcolm X for a 1960 article, “Mr. Muhammad Speaks.”

A few years later, Haley came back to Malcolm X for an in-depth Playboy interview, a feisty back-and-forth that set the table for their collaboration on “The Autobiography of Malcolm X,” published in 1965. “Haley shaped the content of the book to maximize both its sensational value and its commercial success,” Norrell writes.

Malcolm X went through enormous changes during the years of working on the book, breaking with the Nation of Islam over Elijah Muhammad’s sexual activities, and making his eye-opening pilgrimage to Mecca. Malcolm X was assassinated before Grove Press published the book.

” ‘The Autobiography of Malcolm X’ must then be understood as the creation of its subject’s life, not a factual recounting of it,” Norrell writes.

“The Autobiography” was widely praised in reviews, became a bestseller, and is often taught as a classic American autobiography alongside Ben Franklin’s. It also has been scrutinized from many points of view; Norrell notes the late Manning Marable’s criticism that Haley undermined Malcolm’s black nationalism. The book, Norrell writes, “contained sufficient elasticity of meaning to gain a broad and disparate readership.”

“Roots” grew out of a book Haley wanted to write about his family history – and of stories he heard as a boy about his African ancestors. Haley exasperated both his agent and publisher with his research and other delays. (He also got a crucial bit of help from Jan Vansina, a history professor at the University of Wisconsin-Madison.) On a visit to Gambia, Haley talked with a griot whose account of Haley’s ancestor Kunta Kinte cinched the author’s Africa-to-America story. Before he finished writing the book, Haley made a TV deal with David Wolper.

Norrell calls Kunta Kinte “the second great hero” Haley created in writing: “He and Malcolm X were examples of fierce, independent, and manly characters, and together they formed a new and cherished archetype for black Americans – and, indeed, for many whites.”

The bestselling book won a special Pulitzer Prize; Wolper’s TV miniseries galvanized the nation.

But in the wake of this success, Haley faced accusations of plagiarism, only one of which Norrell finds worthy of serious discussion. Scholars and researchers criticized Haley, justly, for factual errors, a situation exacerbated by overreaching statements Haley had made about the book’s accuracy.

Nonetheless, Haley’s books stimulated national discussion. Norrell makes a convincing case that Haley increased, for good, the variety and quality of stories that can be told about its African-American citizens.