For the past several years, Lauren Markham has reported on immigration issues as a journalist; she’s also worked at Oakland International High School in California’s East Bay region, helping coordinate services for immigrant students.

What Markham hadn’t quite realized, she said, was that “under my nose, at this school where I spent four days a week, the number of unaccompanied minors had skyrocketed.’’ The challenges faced by children who come to the United States without parents became the core drama of her book, “The Far Away Brothers: Two Young Migrants and the Making of an American Life.’’

“I had this idea for a book, and I knew that I needed central characters,’’ Markham said. “That spring I met the Flores twins.’’ The Salvadoran teens, whom Markham calls by the pseudonyms Raul and Ernesto, agreed to let Markham tell their story; she visited their hometown five times to research their family and the circumstances that led them to choose the dangerous journey north by themselves.

“What I thought was very interesting,’’ Markham said, “was one, they had very little family support in the United States, so they were really making it on their own, and two, there were two of them — two young men and their relationship in this strange and terrifying new world they found themselves in.’’

Immigration, Markham emphasizes, isn’t just a political hot topic; it’s a timeless human story. “We have a sort of narrow view that immigration is something we have to deal with at the border,’’ she said. “But immigration starts long before the border.’’ Despite the president’s rhetoric, she added, “young people are coming regardless of what Trump is saying or doing. They’re not trying to come to the United States because of what the United States offers; they’re leaving the conditions in their home countries. Walls don’t work. To stop the flow of unaccompanied minors you really have to look at the root causes.’’

Markham will read 7 p.m. Wednesday at Porter Square Books.

Kate Tuttle, president of the National Book Critics Circle, can be reached at kate.tuttle@gmail.com.