When the news broke in July 2011 that an atrocity had been committed in prosperous, peaceful Norway, one of the first things to become apparent was that the perpetrator, Anders Behring Breivik, was something different.

Blond, tall, handsome and muscular, the 32-year-old from Oslo seemed as far removed from the bullied omega males who shoot up classrooms in the United States as he did from the jihadists whom the post-9/11 world usually associates with such large-scale brutality. From his meticulous self-presentations in precrime photo shoots to his defiant demeanour and far-right salutes while on trial, the following year, Breivik seemed more than merely vile: he seemed formidable.

One of Us, Åsne Seierstad's thorough and absorbing account of the Oslo bombing and gun massacre on Utøya island, and the life and trial of the man who perpetrated them, offers an opportunity to look more closely at the fearsome pose adopted by Breivik and see what cracks might show.

There is always a sense of ethical trickiness about a book such as this, especially so soon after the events in question. Does it play into the killer’s narcissistic hands and pour fuel on the ideological flames that his deeds were intended to ignite?

Seierstad, the author of The Bookseller of Kabul, has worked for many years as a journalist in the Arab world. One of Us is her first book about her native country, and in it she proves astute enough to usefully probe what is still an open wound without flinching, even if, by the end, we are only partly closer to understanding the why behind the forensically delineated how of July 22nd, 2011.

Despite Breivik’s Photoshopped efforts to appear as the indomitable Aryan avenger, his early life bears ample evidence of the rejection and emotional impoverishment typical of lone spree killers.

His childhood was marked by neglect at the hands of a depressive mother. His diplomat father left when Anders was young and, when he was 15, cut contact with him entirely. At school he was joyless and solitary, bullying other pupils until one of his victims, a Pakistani immigrant named Ahmed, stood up to him and thence became his friend.

As a teenager Breivik embraced hip- hop culture and became a graffiti tagger. Attempting to ascend the tagging hierarchy from the status of “toy” to that of “king”, Breivik suffered one of the series of rejections that Seierstad implicitly offers as explanation for the rage that would eventually drive him to slay 77 of his countrymen.

But these rejections – being passed over for a local leadership position in the right-wing Progress Party, being slighted by gamers higher up the hierarchy of the online role-playing game World of Warcraft – seem rather ordinary, inadequate to emotionally account for Breivik's decision to commit extreme violence.

Despite his blue-eyed good looks, sexually Breivik was a failure. Later he would attempt to explain his dearth of romantic involvements as a consequence of his hard- working lifestyle. His former friends, however, recall a man who was simply never attractive to women, and who seemed to have little interest in them either. (Several were convinced that he was homosexual.)

Mail-order bride

Breivik’s only noteworthy relationship was with a Belarusian mail-order bride whom he found online. He visited her family and later brought her to Oslo. Their romance did not last long. “She called him a male chauvinist. He called her a gold-digger.” The woman went back to Minsk.

After breaking with the Progress Party Breivik proved successful as an online “businessman”, worrying the borders of legality by selling fake diplomas. When the authorities started snooping around, Breivik took his savings and moved back into his mother’s Oslo apartment.

Holed up in what he called his "fart room" he became entirely absorbed in World of Warcraft. In the virtual world he called himself Andersnordic; he became a guild leader, giving orders to gamers around the world via his headset, ruthlessly dismissing team-mates whose dedication was less than his own. This was serious, he admonished his comrades.

Feeling guilty about how much time he was devoting to WoW, Breivik began reading anti-jihad and anti-Islam websites. He joined discussion boards and absorbed the theories of writers such as his hero, Fjordman (from whom he would quote extensively in his 1,500-page, largely cut-and-paste manifesto).

In particular he became fascinated by Bat Ye’or’s “Eurabia” theory. Ye’or claimed that European leaders had secretly capitulated to the Muslim world in exchange for oil and peace and that Muslims were infiltrating Europe through immigration and high birth rates, with the ultimate aim of enslaving the continent.

In Breivik’s eyes the Islamification of Europe and the undermining of white Christian values was being abetted by “cultural Marxism”, whose lackeys included the Norwegian Labour Party and its Workers Youth League (AUF). Breivik would slay 69 AUF members on Utøya.

Despite her concern for the amount of time that he was spending alone in his room, and the anti-Islamic diatribe that became his sole topic of conversation, Breivik’s mother appears to have had no inkling of the catastrophic path her son was taking. Their relationship was odd: when she separated from her boyfriend of some years, Breivik bought her a vibrator by way of consolation.

In spring of 2011 Breivik moved to a secluded farmhouse, where he began constructing a bomb, rounding up weapons and finalising his terroristic plan.

Grimly methodical

The account of the bombing and massacre is grimly methodical. We watch as Breivik, trained on years of Call of Duty and Oslo gun clubs, strides across the small island, executing dozens of teenagers, some of whom plead for their lives, others who play dead only to be shot through their skulls by an amused Breivik.

In one of the book’s queasiest scenes the steroid-pumped gunman enters a building where many of the youths are hiding. As he starts shooting he is fascinated to find that those yet to be shot do not try to escape but stand frozen on the spot. “I’ve never seen that in a movie,” he later remarked.

To balance what would otherwise be an indigestibly grim book, Seierstad splices Breivik’s narrative with the stories of several of his victims, including young women from a Kurdish family who fled the Iraq war, and an idealistic young socialist who idolised Barack Obama.

One reads these saccharinely rendered sections impatiently and guiltily, eager to get back to Breivik, with his belligerent ideology and bizarre, emoticon-strewn manifesto. The final 100 pages are given to an account of Breivik’s trial – we get the sense of a stunned Norwegian justice system scrambling to accommodate the scale of his crimes – and the aftermath of the killings. Following much controversy, Breivik was judged not to be psychotic and therefore accountable for his actions. He will almost certainly die in prison.

For the most part Seierstad refrains from condemnatory language and emotivism, letting the facts speak damningly for themselves. After 500 pages sifting through the materials of Anders Breivik’s life, though, we are still left wondering what drove a man to step so radically beyond the pale of human community.

Perhaps it would take a novelist’s tools to really penetrate the psyche of an aberration like Breivik, and it may be too early yet for the humanisation that would entail. For now, beyond the facts of his obvious narcissism and barren extremism, Breivik remains a miserable enigma and an ambiguous warning.

Rob Doyle's first novel, Here Are the Young Men, was published in 2014. This Is the Ritual, a collection of short fiction, is due out in 2016