Dina Temple-Raston is the executive producer and host of the “What Were You Thinking” podcast which looks at adolescent decisions, like joining ISIS, and how the developing brain may influence those choices. The first season is now available on iTunes. She is on book leave from NPR where she has been the network’s counter-terrorism correspondent for a decade.

‘We love you both sooo much,” the email from Ayan, 19, and her sister, Leila, 16, to their parents began. “You have given us everything in life. We are eternally grateful for everything.” That was followed by a small heart emoticon. Then the dispatch took an unexpected turn: “We have decided to travel to Syria and help out down there as best we can. We know this sounds absurd, but it is haqq [truth] and we must go.” It was the fall of 2013.

“Two Sisters: A Father, His Daughters, and Their Journey Into the Syrian Jihad” is Adne Seirstad’s retelling of a parent’s nightmare. Translated from the Norwegian by Sean Kinsella, the book provides a meticulous reconstruction of adolescent decision-making at its worst: Two Norwegian sisters conclude that it would be a great idea to leave the tranquility of Norway for an apocalypse in Syria.

As NPR’s counterterrorism correspondent, I have spoken with literally dozens of young people who made similar decisions — whether it was to join the Islamic State or a branch of al-Qaeda — and in almost every instance, they appeared as driven by the confusing buzz of adolescence as they were by the steady drumbeat of ideology. “Two Sisters” appears to have brought Seierstad to a similar conclusion. While she writes that the girls had some sort of religious awakening, their decision to go to Syria, she believes, was also motivated by a “search for identity, meaning, and status; the desire to belong; the influence of others; excitement; the need to rebel; and romantic notions.”

Unpacking violent extremism is familiar territory for Seierstad. Her 2015 book, “One of Us,” told the story of Anders Behring Breivik, the mass murderer who decided that the best way to protest Muslim immigration in Norway was by opening fire on young people attending a summer camp sponsored by the country’s liberal party. Seierstad deftly applies what she learned in “One of Us” to Ayan and Leila’s story.

“Two Sisters,” by Åsne Seierstad; translated by Seán Kinsella (Farrar, Straus and Giroux)

The Jumas arrived in Norway when Ayan was 6 years old and Leila just 3. Their secondary school was in a nice part of town, and the student body was diverse, though “for the most part blond, blue-eyed, and Norwegian through and through.” Their school mates “were preppy, shopped as a hobby, wore Uggs, leggings, checked shirts, and yachting jackets,” Seirerstad writes. Ayan and Leila, who are of Somali descent, carved out their own sartorial path. “Ayan wore turquoise shawls, large earrings, and skinny jeans.”

Leila, on her first day of lower secondary school, “turned up in bright green pants and a red sweater, and wearing large round glasses. . . . She played football in PE class and dived in swimming, and her Facebook profile looked like any other girl’s.”

That effortless assimilation wasn’t welcomed by their mother, who fretted that the girls were becoming “too Norwegian.” Her solution was to band together with other Muslim mothers to hire an Islamic tutor at the mosque — a young man asked not just to teach their children to read the Koran but also to counsel them about how to be good Muslims in the West. The new tutor ends up having a hand in Ayan and Leila’s decision to go from hoop earrings to niqabs.

It would be too simplistic to say that schoolgirl crushes sent the sisters rushing to Syria, but there is little doubt that they were as motivated by the notion of having boyfriends as they were by the idea that tending to an Islamic State fighter — being his wife, having his children — would bring them closer to God.

“The Skype ringtone sounded on her laptop. She clicked on the telephone receiver symbol. They never talked with the camera on. . . . [He] told her about his house and car, life among the other fighters. He asked her to click on the camera icon. She put on her niqab and placed her finger on the symbol. She saw him. He saw her eyes.

“ ‘So how did you become ‘radicalized’ then?’ he asked, in a flirty way. He chuckled softly. . . .

“ ‘Lift your veil, then,’ he said.

“She raised it and showed him her face.

“ ‘Take it off,’ he challenged.

“She took it off.”

Hundreds of young people have left Norway to join the Islamic State in Syria, but what gives “Two Sisters” unusual emotional power is a third character: Ayan and Leila’s father. Sadiq Juma had been a child soldier in Somalia, so he decided that he had enough experience to go to Syria, find his daughters and bring them home. Seierstad is good at re-creating a scene, so we are right there when Juma slips across the Turkish border into Syria. Readers can feel the seediness of the local hotels and will find themselves bristling at the sketchy characters who say they will help the desperate father find his girls.

It is a testament to Seierstad’s storytelling ability that the best part of the book isn’t when Juma finds himself standing in front of his eldest daughter in Syria. That would be too predictable. Instead, the strongest sections involve the unvarnished look we get into a complicated father-daughter relationship.

If I have issues with the book, they involve Seierstad’s journalistic decisions. It turns out that Ayan and Leila are not the Juma girls’ real names, but Seierstad chooses to tell readers that in the final pages of the book. Finding this out so late — after Seierstad convinced me that I understood the sisters so well — made me feel a little snookered. Seierstad also waits until the end to reveal that the account of Sadiq Juma’s experiences in Syria is based almost solely on his version of events. Seierstad writes that she went over his story painstakingly to find any flaws in his recounting, but even so I couldn’t help thinking that may not have been enough. Throughout the book we learn that Juma misleads people to get what he wants. I wondered if he misled Seierstad, too.

But these are quibbles. “Two Sisters” provides an immense contribution to our understanding of how the Islamic State is able to persuade so many young people to abandon their comfortable lives in the West to join its cause in Syria. And in my experience, Ayan and Leila’s journey isn’t unusual, it is the norm. Just a year after the two sisters left Norway, I reported on three schoolgirls from a suburb of Denver who tried to travel to Syria. They, too, had fallen in love with some Islamic State fighters they had met online. Two of the young women were Somali sisters, ages 15 and 17, who had spent most of their lives in the United States.

I visited their schools, talked to their friends, spoke to their teachers, and got my hands on their emails and texts, the content of which, initially at least, wouldn’t have set off any alarms: They talked about boys and makeup and homework. As fate would have it, the story of the Denver girls had a rather happier denouement; they were intercepted by authorities during a layover in Germany and were returned to their parents. It is an ending anyone reading Seierstad’s book would have preferred — Ayan and Leila never return home.

A Father, His Daughters, and Their Journey Into the Syrian Jihad

By Asne Seierstad

Translated from the Norwegian by Sean Kinsella

Farrar, Straus and Giroux. 418 pp. $28