"The Brides of Jihad", "Married to the Islamic State", "Women under the Caliphate"... These are just a few examples of newspaper headlines about the girls and women, hailing from over 50 countries, who joined the extremist group in Iraq and Syria. One woman decided to delve deeper into their stories. Iranian-American writer Azadeh Moaveni travelled across the Middle East, the Mediterranean and Northern Europe to tell the tales of the "gone girls". She has just published a book on the subject, entitled "Guest House for Young Widows: Among the Women of ISIS". She joins us in the studio.