Speer started out as an undistinguished young architect, flattered to be designing the monumentally intimidating public buildings planned for the Third Reich. But his true genius was for organization. As minister of armaments and munitions during World War II, he became one of Hitler’s most powerful lieutenants–and a possible successor. Hundreds of thousands of slave laborers, rounded up by his underling Fritz Sauckel, worked Speer’s factories. Sauckel was hanged; why not Speer? His civilized demeanor? His late-inning attempts to thwart Hitler? His expressed remorse? His remoteness from the extermination program? True, he’d never ordered a single death. They couldn’t even prove he knew.

After his release in 1966 Speer became a celebrity–“a kind of freak,” he told Sereny. Was he a con artist or a changed man? In his best-selling books (such as “Inside the Third Reich”) he denounced what he now recognized as a criminal state, and gave much of the money to charities, including Jewish groups. He studied the Protestant theology of Karl Barth and went on retreats at a Roman Catholic monastery; late in life, his dearest friend was a rabbi. He acknowledged guilt, responsibility, repentance; his spiritual mentors found him sincerely anguished. He even flagellated himself for flagellating himself: to his rabbi friend he once wrote of “that conscience which I continually manage to diminish and repress by superficial overuse.” Speer admitted everything. Except the one thing.

As Sereny admits upfront, she grew to like Albert Speer. Before he died in 1981, it wasn’t unusual for Sereny and her husband to hear a German-accented voice on their answering machine saying “Here Albert.” But she was never charmed away from her fixed purpose: to find out what went on inside this genial, infinitely distant man. During a series of 12-hour-a-day interviews she deliberately kept him in suspense for three weeks before asking what they both knew she’d come to ask. Since much of her book’s force depends upon keeping the reader in suspense for 700 pages, it’s not fair to reveal how Speer chose to answer. But Sereny now believes he wasn’t merely “blocking” what he’d known about his colleagues’ extermination of the Jews: “Speer was living a lie, saw no way of ending it and–I think his one great merit–suffered atrociously under it.”

How had a man with such spiritual capacity become, as Sereny says, “morally extinguished”? Speer’s former secretary knew: by giving himself over to Hitler “body and soul.” Some fled to get out of range of Hitler’s magnetism; with Speer the attraction was mutual. “I wouldn’t know how to describe to anyone Hitler’s apparent lightness of spirit when they were together,” the secretary told Sereny, “or the quality of Speer’s concern for him.” In 1975, the German psychoanalyst Alexander Mitscherlich wrote of their"homo-erotic (not sexual) relationship," in which the handsome, ascetic Speer became Hitler’s idealized other self and Hitler Speer’s fatherly protector; Speer himself acknowledged to Sereny that Mitscherlich “came closest to the truth.”

And what made Speer vulnerable? Sereny found that out, too: his parents (like Hitler’s) specialized in emotional deprivation. Does a man grow up to turn away from the deaths of millions because his parents turned away from him? As Sereny tells it, it makes all the horrible sense in the world. Speer’s story suggests that the denial of empathy is the essential crime against humanity, and that love–whether held back or let loose–is a passion more terrifying than we ever wanted to know.