Born in Cleveland, Ohio and raised in San Francisco, she earned a degree in communications from San Francisco State University. Zarr grew up as an Evangelical Christian, a faith with which she still associates though she lives in a predominately Mormon community. Her first three manuscripts were never published, but after winning the Utah Arts Council best young-adult novel of 2003, she was able to find an agent who successfully sold Story of a Girl as the first of a two-book deal.

Inspired by the kidnapping of Elizabeth Smart and Zarr's Christian roots, Once Was Lost addresses issues of faith, identity and home. The title comes from the hymn Amazing Grace written by John Newton. While the characters are Christian, the book was published for a mainstream audience and neither promotes nor criticizes organized religion.

In 2008, Zarr contributed to the YA for Obama project started by fellow YA author Maureen Johnson. Zarr's articles included "Red State Jesus Freaks for Obama" and "Personal Sacrifice."

Standalone Novels

• 2007 ... Story of a Girl
• 2008 ... Sweethearts
• 2009 ... Once Was Lost

Zarr also reads the audio version of her books.

Short Fiction

• "This Is My Audition Monologue" appears in Geektastic: Stories from the Nerd Herd, edited by Holly Black and Cecil Castellucci, 2009

Essays

• "It Is Good" appears in Does This Book Make Me Look Fat?, edited by Marissa Walsh, 2008
• "Who Is My Mother, Who Are My Brothers?" first appeared in Image, and appears in Jesus Girls: True Tales of Growing Up Female and Evangelical, edited by Hannah Faith Notess, 2009