(Duke University)

In the years since 9/11, the Unabomber — that bearded intellectual hermit who conducted his campaign of terror via the U.S. Postal Service — has come to seem a quaint relic. But the almost-simultaneous publication of his prison letters and his brother’s memoir suggest that he remains as relevant as ever.

Twenty years have passed since the Unabomber was unveiled to federal authorities as being a man named Ted Kaczynski. The tipster was Kaczynski’s younger brother, David. No one will ever be able to accuse David Kaczynski of desiring to profit from his betrayal of Ted. At the time that his information provided the solution to one of the longest and most expensive manhunts in U.S. history, David Kaczynski insisted upon his own anonymity (a condition the FBI agreed to before his name was leaked).

His belated memoir, “Every Last Tie: The Story of the Unabomber and His Family,” is remarkable for its slenderness, humility and tact. The book offers a movingly clear portrait of its author; less fully delineated is its portrait of its subject.

Kaczynski, who in the years since his brother’s arrest has made a related but distinct name for himself as an anti-death­penalty activist, is so self-effacing that he both opens and closes his book with the insistence that he deserves no credit for bringing his brother to justice. (That honor, he tells us, goes to his wife, Linda.)

Between these self-deprecating bookends, Kaczynski devotes a thoughtful, affectionate chapter to each member of his immediate family. “Life Force” describes his mother, Wanda, whom Kaczynski recalls teaching him the meaning of the words “humanitarian” and “empathy” when he was barely 6 years old. “Ghost Within Me” recalls Ted Kaczynski Sr., the handsome, warmhearted “gadfly” who ruled “based on reason and dialogue” and said things like “it’s a matter of principle that we respect the law” when David begged him to buy fireworks. “North Star” is devoted to Linda, whom Kaczynski met in childhood and loved from afar for decades.

The Kaczynski family, from left, Wanda Kaczynski, Teddy Kaczynski, Ted Kaczynski Sr. and David Kaczynski outside their home in Evergreen Park, Ill. in 1952. (Courtesy of David Kaczynski)

Only Kaczynski’s opening chapter is dedicated particularly to Ted Jr. The chapter’s title, tellingly, is “Missing Pieces.” It does a fine job of laying the groundwork for a detailed consideration of its subject to follow, but this detailed consideration never comes. This is due in part to the book’s unconventional organization. Because Kaczynski has arranged his material by family member, it’s often hard to follow the chronology of events. And the narrative is not just elliptical, but highly fragmentary; perhaps fearing that he’ll try his reader’s patience by relating aspects of the story we already know, Kaczynski vastly overcompensates. He remains guarded even when writing about periods of Ted’s life to which David is now the sole surviving witness.

Kaczynski does share a few moving anecdotes about the much-older brother (seven years) he frankly idolized. Ted teaches little David that you don’t refer to your “best” baseball player: You call him your “favorite.” When toddler David proves unable to open the back door, Ted improvises a David-height handle out of a spool, which remains nailed to the door for years after David has outgrown it, a testament not just to Ted’s affection but his cleverness.

David Kaczynski also allows himself to open up about a few of his brother’s less-flattering moments. In one, a teenage Ted tries to frighten his parents by deliberately failing to come home from school and then laughs at their anguish. Even more telling, while working a job David helped him obtain, Ted pursues and then sexually harasses a woman, anonymously posting nasty limericks about her in the workplace. Horrified, David gets Ted fired, in a strange and sad rehearsal for the role he’ll later play when he unveils his brother as the murderous author of the Unabomber “manifesto.”

And so “Every Last Tie” does offer moments of revelation. What is missing is depth and synthesis. Because David Kaczynski doesn’t provide a basic timeline of the family’s life, even the fascinating cache of family photos doesn’t reinforce the book’s assertions but rather adds to its mysteries. What are Ted and Dave doing in Iowa? When did the family live in Lombard, Ill.? The most pressing mystery is how the clean-cut, handsome Ted, lying on the couch of his parents’ home reading in 1979, turns into the unkempt woodsman Ted, striking an unnaturally stiff pose, chin tipped up as if in a mug shot, in a photograph taken just three years later. In very short order he would viciously break with his family and retreat to Montana, where he would live until the time of his arrest almost two decades later. Somehow, in the life of this brilliant but uneasy man, a fateful shift had occurred that would terrorize a nation, cost multiple lives and an enormous number of investigative dollars, and tear an ordinary family to pieces.

This is the fateful shift David Kaczynski is least able to illuminate. Instead, he emerges from these pages as someone who palpably delights in relating those moments that show his loved ones in the best possible light. This tendency makes him a very sympathetic writer, but it doesn’t make him the best chronicler of a career terrorist and serial killer or analyst of that person’s effect on his horrified and heartbroken family.

He avoids considering connections between his brother’s well-documented brilliance and his crimes. The same goes for the many signs that Ted was mentally ill and for the evidence that Ted suffered trauma while hospitalized in infancy and while enrolled in a series of notorious psychological experiments as an undergraduate at Harvard. These factors are scattered across the pages of “Every Last Tie,” but they’re not marshaled into a story. We can hardly expect David Kaczynski to definitively explain his brother, but, given his perspective, we might be forgiven for hoping he’d speculate.

Two fascinating stories might have been told here, the story of the brilliant man who becomes a murderous madman being only the most obvious. The other is a story of two very similar brothers. Both are handsome, talented, intelligent and cherished by their parents. Both prize the life of the intellect, nature and integrity. Both leave society behind to commune with the wilderness. In midlife, one becomes a notorious serial killer, the other a vegetarian Buddhist. The first story — why Ted didn’t turn out like David — is the one “Every Last Tie” leads us to expect. The second — why David didn’t turn out like Ted — is the one that I ended up wanting to read. David Kaczynski steers clear of them both. Perhaps in another 20 years he’ll be ready to tell them.

Susan Choi is a novelist whose books include “My Education” and “A Person of Interest.”

On Saturday, David Kaczynski will be at Politics and Prose, 5015 Connecticut Ave. NW, Washington.

every last tie
The Story of the Unabomber and His Family

By David Kaczynski

Duke University. 176 pp. $19.95