They were the darkest of the late-1970s U.K. bands, skyrocketing to fame after their lead singer hanged himself in 1980 to become one of the most bootlegged bands ever. But Joy Division’s greatest enigma may have been its name — a reference to the brothel at Auschwitz as depicted in the book “House of Dolls” by Ka-Tzetnik 135633 (Yehiel De-Nur).

That sinister fact, while lost on the new kids sporting their ubiquitous “Unknown Pleasures” T-shirts — among them Iggy Azalea, Kristen Stewart and the members of One Direction — has only added to the band’s mystique. Other doom-and-gloom acts from the period may have spouted nihilistic lyrics and quoted Existentialists such as Albert Camus and Jean-Paul Sartre, but no one else compared their sense of despair, isolation and self-loathing with that of a Nazi sex slave, as Joy Division did in its first single, “No Love Lost.” Its cover depicted a Hitler youth member beating a drum. The B-side, “Warsaw,” recounted the story of Nazi deserter Rudolf Hess, who fled to Scotland.

So, how did a this handful of young non-Jews from Manchester, England, become obsessed with the Holocaust? Thirty-five years after the band’s breakup, two new books shed light on the odd connection.

In the introduction to “So This Is Permanence,” a collection of the writings of the late singer Ian Curtis, the book’s editor, Jon Savage asserts that Joy Division did not exploit the Nazi era, as so many of its punk peers did. Rather, its members seemed profoundly and genuinely moved by the Holocaust.

The Sex Pistols wore swastikas and SS uniforms with fetishistic zeal, serving up crude, salacious tracks like “Belsen Was a Gas” for pure shock value. The Ramones wrote fast, furious ditties like “Blitzkrieg Bop” and “Today Your Love, Tomorrow your World” that only obscurely referenced the Nazis. Before his death in July, Tommy Ramone (born in Budapest as Tamás Erdélyi), attributed the band’s frenzied sound to his own outsider status as an Eastern-European Jewish refugee and the child of Holocaust survivors. In the tough leather jackets of The Ramones, delivering three-chord battle chants, Erdélyi was able to morph from victim to victor and to rebel against his traumatic past.

But the reason for Joy Division’s fascination with World War II was the exact opposite: Its members were attracted to the trauma, plunging into its depths with great sympathy for its victims.

Savage links the band’s interest in the Holocaust to the advent of “pulp history” in the 1970s, when paperbacks such as Sven Hassel’s Wehrmacht and SS novels were churned out with abandon and sold at cult stores like Paperchase and Grassroots in London. Manchester boasted a few of its own legendary booksellers, among them House on the Borderland, which Curtis frequented. An autodidact, Curtis’ rapacious reading led him to Antonin Artaud, Hermann Hesse, William S. Burroughs and J. G. Ballard. Growing up in a bleak industrial city at the height of England’s recession, Curtis could relate to these writers’ apocalyptic moods and feverish futuristic visions. But it was the torturous novella by De-Nur, who is remembered by many for fainting while testifying at the Eichmann trial, about a Polish Jewish girl who ends up as a sex slave in Auschwitz, that really clicked.

In his memoir “Chapter and Verse,” former Joy Division guitarist Bernard Sumner claims he was the one who turned Curtis onto the book. “I came across a reference to a section where women were housed for the pleasure of Nazi officers on leave,” he writes. “It was known as the Freudenabteilung, the Joy Division, and that phrase just leapt out at me immediately as the perfect name for the band.”

Sumner, who went on to form New Order, another Hitler reference, acknowledges that it was the punk zeitgeist that enabled the band to consider such a “dodgy” name, because “it was acceptable to be unacceptable.” But outrage for outrage’s sake wasn’t the goal. “For me, it seemed to meet all the criteria we were looking for: our sound, our image, even the way the words looked physically on paper,” he writes, before adding that the controversial name might land them in hot water. “It didn’t mean we were Nazis or had any kind of sympathy with them, because we didn’t. ... Now, in my more mature years, I probably wouldn’t pick it, because I know it would offend and hurt people, but back then, I was very young and well, selfish. Calling ourselves Joy Division was a bit mischievous.”

That may be his take, but naughtiness had nothing to do with Curtis’ decision to troll the story of the infamous block 24 at Auschwitz, writes his widow Deborah in “So This is Permanence.” The tormented singer-songwriter had always been a history buff. Deborah describes meeting him in 1972, shortly after he won school prizes in history and divinity. He showed her his black binder, divided into categories for “lyrics” and “novel,” and saw how serious he was about prose, poetry and his creative aspirations. They began dating and married shortly after. Deborah recalls how deliberately he chose every element in their home, particularly his writing room, where he’d retire every night, scrawling in a plume of smoke, burdened by the weight of history.

“Ian’s art was crucial to him,” she writes in the forward. “ He did not consider songwriting a mere commercial endeavor. So it was unsurprising he turned to darker, more serious subjects to inspire him. Not specifically the Holocaust, but war itself.”

Ian’s father had served in World War II, which may have led to his initial fascination, Deborah maintains. But it was his deep empathy for the suffering of others that allowed him to identify with Holocaust victims. It’s fair to say he was also morose, a quality underscored by his deep drone of a voice. But it was Curtis’ sense of compassion that enabled him to come up with the relentless lyrics of “No Love Lost,” about a sex slave’s forced sterilization or abortion:

“In the hand of one of the assistants, she saw the same instrument which they had that morning inserted deep into her body, She shuddered instinctively. No life at all in the house of dolls. No love lost. No love lost.”

The song also contains a spoken-word part entirely lifted from “House of Dolls.” In “So This Is Permanence,” Curtis’ handwritten notes for the song begin with the heading “House of Dolls.”

Other early tracks, like “Conditioned” and “Crimes Against the Innocent,” delve into similar themes — shame, guilt, frustration and pain, set to stark, mournful soundscapes that echo with pain. But as Savage explains, Curtis pushed music beyond punk’s sensationalist rebelliousness, its explosion of anger and pent-up emotions directed at an unspecified “you.” His lyrics were a first-person retelling of horrific situations in which he assumed both complicity and powerlessness. Like De-Nur, he pictured himself in the musical retelling of atrocities.

“The assassins all grouped in four lines / I did everything, everything I wanted to / I let them use you for their own sake.”

Was he drawing a parallel between World War II and the futility of England’s youth at the time? Or were those lines a betrayal of his own conflicting emotions — of feeling trapped, helpless, both violated and violator.

The cover of Joy Division’s debut EP, 'An Ideal For Living.'

After all, he had more on his plate than most in their early 20s. He was married and a father, forced to keep his day job at an employment agency, working all night to fulfill his creative aspirations and torn apart by an extramarital affair. Further compounding his personal sturm und drang was epilepsy. His seizures became so severe and frequent that they threatened to derail his performance ability. In fact, one of Joy Division’s hits, “She’s Lost Control,” was based on a young woman he had counseled who had an epileptic seizure in his office. He called her employers later to check in on her, only to discover that she had died as a result of a seizures. In her plight — and that of the abused, defenseless sex slave at Auschwitz — he saw his own. Curtis killed himself on the eve of what would have been Joy Division’s first U.S. tour, just shy of his 24th birthday, enshrining him into cult status among angst-ridden teens everywhere.

It would be easy to view Curtis’ untimely demise as a cautionary tale against taking on weighty issues like the Holocaust. The truth can set you free, it’s often said, but it can also be too much for some to bear. Curtis’ inner turmoil made him both particularly attuned to the suffering of the sex slaves at Auschwitz and their most unlikely conduit. Unfortunately, the message wound up killing the messenger.

But Savage sees the singer-songwriter’s great gift of being able to address world tragedies and transmit them creatively as a legacy that’s uplifting and humanitarian, most likely the reason why Joy Division’s songs still resonate.

“Distilled emotion is the essence of pop music, and just as Joy Division are perfectly poised between white light and dark despair, so Curtis’ lyrics oscillate between hopelessness and the possibility of, if not absolute need for, human connection,” Savage concludes.