A novel about a mother's hatred for her son won the tenth Orange Prize for Fiction on Tuesday night. Lionel Shriver was awarded the £30,000 cheque for her seventh book, We Need to Talk About Kevin.

American-born Shriver's book was low on the list of favourites for the women-only prize. The other contenders were Old Filth by Jane Gardam, the bookies' favourite, Billie Morgan by Joolz Denby, A Short History of Tractors in Ukrainian by Marina Lewycka, Liars and Saints by Maile Meloy and The Mammoth Cheese by Sheri Holman.

Told in the form of letters from Eva Khatchadourian to her estranged husband, We Need To Talk About Kevin probes the nature/nurture question as Eva considers her own culpability for her son's Columbine-style high school massacre.

Jenni Murray, chair of the judging panel, praised the book as "courageous". "We Need to Talk About Kevin is a book that acknowledges what many women worry about but never express - the fear of becoming a mother and the terror of what kind of child one might bring into the world," she said. "It will resonate with everyone who has had a child or thought about having one."

Shriver, who changed her name from Margaret to Lionel at 15 because she believed men had better lives, is published by Serpent's Tail, a small, independent publisher. Her book has sold more than 1,200 copies in the UK and about 50,000 in the US.

The prize was awarded at a ceremony in central London. As well as the cheque, Shriver received a limited edition bronze sculpture known as a Bessie.

The Orange Award for New Writers, launched this year, went to Diana Evans for her novel 26a. Evans received a £10,000 bursary from the Arts Council England.

Later this year, Orange is running a "best of the best" award for the past 10 years of the prize. Past judges and the public will pick the winning book on October 3.