NEW YORK - Nadia Murad was captured, beaten and sold as a sex slave by Islamic State militants, a harrowing experience she would clearly like to put behind her, but she is telling her painful story in a new book published on Tuesday.

In "The Last Girl," Murad recounts her life in a northern Iraqi village, her brutal captivity, tension-filled escape and feelings of betrayal and abandonment by those who failed to help.

Murad is Yazidi, a religious minority who lived in an uneasy existence with their Muslim neighbors. In 2014, she was one of about 7,000 women and girls captured by the hard-line Sunni Muslim fighters who view Yazidis as devil worshippers.

Yazidi men and older women, including her brothers and her mother, were killed. The younger women and girls were held in captivity for sex.

"It never gets easier to tell your story. Each time you speak it, you relive it," Murad writes in the book.

"(But) my story, told honestly and matter-of-factly, is the best weapon I have against terrorism, and I plan on using it until those terrorists are put on trial."

United Nations investigators estimate more than 5,000 Yazidis were rounded up and slaughtered in the 2014 attack, and U.N. experts have said Islamic State was committing genocide against the Yazidis in Syria and Iraq.

In September, the U.N. Security Council approved the creation of an investigative team to collect, preserve and store evidence in Iraq of acts by Islamic State.

International human rights lawyer Amal Clooney, who represents Murad and wrote the foreword to "The Last Girl," is campaigning for the Islamist group to be prosecuted through the International Criminal Court.

Murad was abducted at age 21 from the village of Kocho near Sinjar, an area home to about 400,000 Yazidis.

"Our Sunni neighbors could have come to us and tried to help," she writes. "But they didn't."

Recounting the seemingly endless rapes by men who bought and sold her was clearly difficult for the soft-spoken Murad.

"At some point, there was rape and nothing else. This becomes your normal day," she says in the book.

"You don't know who is going to open the door next to attack you, just that it will happen and that tomorrow might be worse."

To escape, Murad saw a fleeting chance to jump over the garden wall of her captor's house in Mosul. After wandering the streets cloaked in an abaya, she made a daring decision to knock on the door of a stranger's house and ask for help.

That was a huge risk, and she later learned her niece, also enslaved, had been turned in six times to Islamic State by people she had asked for help.

"Families in Iraq and Syria led normal lives while we were tortured and raped. They watched us walk through the streets with our captors," she writes. "They let us scream in the slave market and did nothing."

Murad was lucky that the strangers she found in Mosul helped smuggle her to a refugee camp.

With publication of her memoir by Tim Duggan Books, Murad says she wants to see Yazidis in captivity released, the resettlement of survivors, the removal of landmines in the Sinjar region and prosecution of Islamic State.

But more than anything else, she says: "I want to be the last girl in the world with a story like mine."

She now lives in Germany and has become a campaigner on behalf of the Yazidi community. This year she became a U.N. Goodwill Ambassador for the Dignity of Survivors of Human Trafficking.

(Reporting by Ellen Wulfhorst, Editing by Ros Russell; Please credit the Thomson Reuters Foundation, the charitable arm of Thomson Reuters, that covers humanitarian news, women's rights, trafficking, property rights, climate change and resilience. Visit http://news.trust.org) ((ellen.wulfhorst@thomsonreuters.com; 646-223-6283; Reuters Messaging: ellen.wulfhorst.thomsonreuters.com@reuters.net))