In 1996, Joan Didion unholstered the X-Acto knife that was her pen and went to work on Bob Woodward. In a register of pitiless irony, she quoted Woodward’s earnest explanations of his journalistic methods—the difference between “background” and “deep background,” his “eight file drawers” of documents for a book on the Supreme Court. She was unimpressed. “These are books in which measurable cerebral activity is virtually absent,” Didion wrote. In the end, she determined that Woodward was engaged in the writing of “political pornography.”

This was unfair, at best a category error. What Didion failed to note was that Woodward was a reporter, not a scholar or a belletrist, and that before he was thirty he, with his Washington Post partner, Carl Bernstein, had unearthed the predations of the Watergate scandal—hardly the work of stenographers in thrall to power. It brought down the Presidency of Richard Nixon. Journalism is a first rough draft of history, as they say, and scholarship, which feeds on journalism and so much more, plays by another clock. Robert A. Caro began the research for his multivolume biography of Lyndon B. Johnson half a century ago.