The Sunday Times of London has called Robert Caro “one of the great reporters of our time and probably the greatest biographer.” If I were to revise that sentence, I would remove the word “probably.”A painstaking researcher, Caro has written biographies of only two people, master builder Robert Moses and President Lyndon Johnson, the latter in a series not quite complete. In his 2019 book, “Working,” Caro describes the lengths to which he would go to confirm or deny a story.