* A.M. Homes wins 2013 Women's Prize for Fiction
* Mantel fails to win on third nomination
* Winning novel a tale of American dream gone wrong
The American novelist A.M. Homes beat double Man Booker Prize-winner Hilary Mantel to the 2013 Women's Prize for Fiction on Wednesday with a tale of murder, sibling rivalry, adultery and absolution.
Homes's "May We Be Forgiven", which follows a violent change in the lives of a historian and his high-flying younger brother, secured the 30,000 pound ($45,900) award for Homes despite bookmakers heavily favouring a triple sweep for Mantel's bestselling "Bring Up the Bodies", already winner of the Booker and Costa awards.
The chair of the judges, Miranda Richardson, said the panel argued long and passionately over a shortlist that also included former winners Briton Zadie Smith and U.S. novelist Barbara Kingsolver, as well as U.S. screenwriter-turned-novelist Maria Semple and British writer Kate Atkinson.
"But in the end we agreed that 'May We Be Forgiven' is a dazzling, original, viscerally funny black comedy - a subversion of the American dream," she said.
The darkly comic story follows the historian Harold Silver, who has spent a lifetime watching his taller, smarter and more successful younger brother George acquire a covetable wife, two children and a beautiful home in New York.
But George has a murderous temper and when he loses control the two brothers are hurled into entirely new lives in which they must both seek absolution.
Homes, whose first name is Amy, writes most of her novels from a male perspective. They are often laced with violence and sex and mixed with black humour.
"I find it harder, self-consciously so, to write a female narrator," the author, whose other works include "This Book Will Save Your Life" and "The End of Alice", told the Guardian newspaper last year.
The British bookseller Foyles said "May We Be Forgiven" was a "crowning achievement" for Homes that put her among contemporary American greats such as Pulitzer prize-winner Cormac McCarthy and "Independence Day" author Richard Ford.
"It's a powerful exploration of where the American dream went wrong, laced with sharp observation, pathos and dark humour," Foyles said in a statement.
British bookmakers William Hill had made Mantel odds-on favourite to win the prize with her 11th novel, her third appearance on the Women's Prize shortlist. Homes and Zadie Smith's "NW" were joint second.
Mantel won the Booker in 2009 for "Wolf Hall" and in 2012 for "Bring Up the Bodies", the first two books in a trilogy about the rise and fall of the 'eminence grise' Thomas Cromwell in the court of King Henry VIII. She won the 2012 Costa Book Award in January.
The Women's Prize for Fiction, previously known as the Orange Prize for Fiction, was set up in 1996 to promote fiction written by women.
It is awarded to the best novel of the year written in English by a woman.
Homes joins a celebrated list of previous winners, including Madeline Miller for "The Song of Achilles" in 2012, Téa Obreht for "The Tiger's Wife" (2011) and Lionel Shriver for "We Need to Talk About Kevin" (2005).