A radical move

On an unremarkable October morning in 2013, two Norwegian teenagers of Somalian descent - Ayan Juma, 19, and her sister, Leila, 16 - woke up early, dressed and, without telling a soul, boarded a flight to join ISIS fighters in Syria.

"We love you both sooo much," they later wrote to their parents in an email festooned with heart emojis. "Inshallah this decision will help us all on the day of judgment."

They had been planning the secret journey for a year. Their goal, according to Ayan, was to flee home, marry and die. Their father set off after them, tracking them across ISIS territory - razed towns rank with rotting corpses. He was captured and brutally tortured.

Two Sisters, a new book by Norwegian journalist Asne Seierstad and translated by Sean Kinsella, begins in the aftermath of the girls' departure, which stunned their family and tight-knit Somali immigrant community: What had gotten into their girls - so educated, so adored?

When Sara and Sadiq Juma arrived in Norway, Ayan was six and Leila three. Sara and Sadiq saw their daughters "dabble in fundamentalism," as Seierstad puts it. They were taking Quran classes with a militant new teacher and begged to be allowed to wear niqabs. But they were otherwise tractable, polite - never in danger of becoming too Norwegian, Sara thought with satisfaction.

This is Seierstad's second investigation into radicalisation. One of Us (2015) told the story of Anders Behring Breivik, who murdered 77 people in Norway in 2011, most of them teenage members of a left-wing political youth organisation. He said he was protesting Muslim immigration and Norway's embrace of feminism.

One of Us is a masterpiece of reportage, design and empathy. By so scrupulously showing us what happened, Seierstad enables us to understand why, how the seeds of grotesque political violence can so often be traced to decidedly apolitical, deeply private personal humiliations.

Seierstad seems to set herself the same task in Two Sisters. "For me, the most important question was: How could this happen?" she writes. But then, she demurs: "I offer no explanation, neither of what attracted them to Islamic radicalism nor what propelled them out of Norway. I relate my findings. It is up to each reader to draw his or her own conclusions."

It's a puzzling disclaimer, not least because any organisation of facts, however simple, always requires - and reveals - an argument. And what we receive is, in fact, an elaborate narrative, full of explicit heroes and villains, written, she tells us, at the behest of the girls' father, Sadiq. "I want people to recognise the danger signs," he said. "We were blind. We thought it would pass. Now we know better."

This admission is tucked away at the very end, in an afterword. It explains the prickling feeling you might have while reading the book that information is being withheld, that Seierstad knows more than she's telling. Sadiq's influence over the text also explains why he is such an outsize figure in the narrative and perhaps why his account is not subject to more scrutiny, given what an unreliable narrator he is - particularly, Seierstad shows us where journalists are concerned.

Seierstad is at her best when she pans out to consider the variety of reasons Western women join ISIS (by 2013, there were 3,000 Westerners in Syria, several hundred of them women), drawn by a hunger for sisterhood, adventure and membership in a society they felt was colourblind - where shared allegiances were more important than race. She evokes the life they find in ISIS-controlled territory in Syria - where boys are taken from their parents at 10 and placed in camps to be trained in combat, their final test being an execution.

She quotes message boards where women wrote about their new lives: the houses given to fighters for free; groceries and stipends delivered monthly; free medical care. The sisters boasted to their brother about their large house and garden, their pet rabbits. As Sadiq survived imprisonment in a fetid latrine, the daughters he was risking everything to save were making pancakes in Raqqa, with sugar topping.

But in general, the sisters and their transformations remain hazy, especially the strong-willed Ayan. At one point, her school essays sound like outtakes from SCUM Manifesto, by radical feminist Valerie Solanas. In a piece entitled 'Women's Liberation', Ayan wrote: "What's worse, we have to give birth to little rat males who we look after and hold dear, right up until they turn from boys into men who in turn go on to oppress yet another woman." And, yet, a few years later she defended the rape of Yazidi and Kurdish women by ISIS fighters: "They're not women," she told a friend. "They're spoils of war."