"The Mother: The story of Wenche Behring Breivik" is based on hours of interviews carried out with Breivik's mother by the journalist Marit Christensen.
The book describes how, a few days before Wenche Behring Breivik died of cancer in March, she was taken to visit her son in prison. Unusually, the prison guards allowed Anders Breivik to come round the glass that had divided them on previous visits.
He put his arms around her and hugged her. "Sorry that I have ruined your life," he whispered, according to Christensen.
According to the book, Wenche Breivik felt guilty and feared a revenge attack in the months after her son's attacks.
"I hate him," she said of her son after she had been released from the psychiatric hospital which she was checked into immediately after learning of what her son has done.
Anders Breivik lived with his mother in the five years leading up to his twin terror attacks, which left 77 people dead, and did much of the planning and preparation in her flat.
However, according to the book, his mother never suspected anything, believing him when he explained the rifle and shotgun he had brought by claiming to have taken up hunting.