First daughter Jenna Bush is writing a nonfiction book for young adults, "Ana's Story: A Journey of Hope," that will center on a 17-year-old single mother who is HIV positive. Based on her time working for UNICEF, the UN children's agency, the book will be published this fall by HarperCollins. "I have been inspired by my work with adolescents in Central and South America," Jenna Bush said in a statement released by her publisher on Tuesday. "These young people have faced extreme hardships and exclusion but are strong in spirit and have an incredible will to succeed. Through their stories, it is my hope to motivate young Americans to increase their awareness of other young people around the world: to learn about the challenges they face, how they triumph over adversity, and to become involved in helping them."