Joyce Maynard (MICKE Sebastien/Getty Images)

Joyce Maynard’s new novel, “After Her,” follows two teenage sisters living in the shadow of Mount Tamalpais in northern California during a spate of killings of young women by a serial killer in 1979. Best known for “At Home in the World,” her controversial memoir about her affair as an 18-year-old with J.D. Salinger, Maynard says this novel looks at familiar obsessions for her: family and the coming of age of a young girl. Maynard spoke from a cottage in New Hampshire, where she is vacationing.

Tell us about the different moments and events that led to “After Her.”

I had known there had been a serial killer on Mount Tamalpais, and it felt so incongruous in such a beautiful, peaceful spot. But the triggering event was when two women showed up for a memoir-writing class I teach in my living room, which looks out on Mount Tamalpais. Over the course of the day, one of them revealed that she was the daughter of the chief homicide detective who had led the investigation. I got to know them and their story, and I asked if they would consider letting me create a work of fiction about a family that resembled theirs in some important ways. It was more complicated than them just saying, “Yes, you can write our story.” They gave me free rein to change it as I chose. I took a lot of license — the story was completely transformed — but at the core is the emotional truth of what their family lived through and what they lived through as girls just coming into adolescence.

I found the evocation of the world of a 13-year-old girl quite effective. Do you think this is an especially important moment in a girl’s life?

I go back and back to that age group. I’m still very much in touch with my young self. It was not a big leap for me to enter the head of a 13-year-old girl. I hope that I’ve written a story that has some real thriller aspects, with suspense and drama, but ultimately what the book is about is the extraordinary vulnerability of these girls. And it happens to be set against the backdrop of these murders. What interested me is the magical, fantastical thinking of a 13-year-old who actually supposes that she knows who the killer is and who imagines that her plan to catch the killer could work. Part of what I wanted was to tell the story of brave girls, relying on themselves and each other.

"After Her" by Joyce Maynard (William Morrow)

You wrote recently that you’re interested in the “wild card of human sexuality.”

I’m interested in all the different ways that people’s sexuality gets expressed, in either a healthy or damaging direction. And I am interested in secrets. I don’t have to look hard to understand why. I grew up in a family that had a lot of them. That left me phobic about what doesn’t get talked about, and sex is one of the big things that doesn’t get talked about. This girl is dealing with her own coming of age and this whole new set of feelings inside her that are healthy and natural, at the same time that this very violent, dark, twisted thing is going on all around her. And her father — who is supposed to be the big protector — is not protecting her and is not able to protect the women getting murdered. She’s just trying to make sense of it all.

Also important to the book is this unusually close relationship between the sisters.

I love that. I didn’t have that with my sister. You write about what you know, and you write about what you want to know.

Burns, editor of “Off the Page: Writers Talk About Beginnings, Endings, and Everything in Between,” teaches creative writing at Cardiff Metropolitan University in Wales.