Amsterdam: When he read the 40-page sample of Astrid Holleeder's memoir Judas in the spring, Dutch publisher Oscar van Gelderen said he knew he had sensational material in his hands.

A gangster boss who has become a celebrity criminal. A sister who knows his secrets, and fears for her life. A criminal justice system unable to keep him behind bars without her help. And the back story of a childhood that was "dysfunctional to the max", van Gelderen said.

Holleeder is the sister of Willem Holleeder, convicted of the 1983 kidnapping of Dutch beer millionaire Freddy Heineken. He has been in and out of prison for years, but never for murder, though Astrid Holleeder calls him a "serial killer" in her book.

Because she got close enough to tape her brother and agreed to testify against him, he is on trial again, this time facing six counts of murder and two counts of attempted murder.

Van Gelderen's instincts were right. The book, released in early November, has been the No.1 bestseller in the Netherlands for seven straight weeks, according to the Dutch book-publishing association CPNB. Rights have already been sold for publication in Danish, German and Swedish, and Little, Brown and Co. in New York bought worldwide English-language rights this month.

Judas is not a recounting of Willem Holleeder's famous misdeeds, but the story of a childhood that included regular beatings by an alcoholic father, and later of Willem Holleeder's mafia-style hold on his family.

"In the writing, there's this strangling feeling of a guy who is controlling everybody," van Gelderen said.

Astrid Holleeder, 51, a successful criminal defense lawyer, describes in chilling detail how, a year after their father's death in 1991, Willem Holleeder was released from prison and took his place as the family abuser. She recounts how painful it was to interact with him after the murder of her brother-in-law, Cor van Hout, Willem Holleeder's longtime friend and co-conspirator in the Heineken kidnapping. She contends that Willem Holleeder ordered that killing, and plans to testify to that effect in court.

Astrid Holleeder has been observing the success of her book from the secret location where she has been living under protection since February, after an inmate in a maximum-security prison described being contracted by Willem Holleeder to arrange for the killing of Astrid Holleeder as well as her sister, Sonja Holleeder; and a Dutch crime reporter who helped Astrid establish contact with police.

Astrid Holleeder agreed to speak with The New York Times only from a secure location, and she said that she did not think she would ever be safe as long as her brother was alive.

"He will not rest until we're dead," she said. "It's about his pride. He cannot let his little sister take him down."

Astrid Holleeder said that she wrote the book as a kind of "last will and testament" for her daughter, who is 31 and has two children of her own. She said that testifying in court during the pre-trial phase of the current case had so far felt ineffectual. (The trial is scheduled to begin in early 2017.)

"I want to tell everything, but they haven't given me the chance yet," she said. "The book is just about how I feel, how we grew up, what in fact made me and my brother into the opponents that we are now."

Even when the 570-page manuscript was finished, Lebowski Publishers did not provide details of its contents to bookstores, for fear that Willem Holleeder would try to prevent its release. But after the publisher disclosed information on a late-night television talk show the day before publication, the first print run of 80,000 copies sold out immediately.

About 400,000 copies of the book have been bought so far – a milestone in a country of about 17 million, where sales of 5000 copies are considered strong.

Judas is a narrative in the present, with flashbacks to the Holleeders' childhood. The account begins in January 2012, when Willem Holleeder was released from prison after serving six years of a nine-year sentence for extortion. Astrid Holleeder said she acted as a kind of consigliere for her brother – advising him on legal matters, arranging his safe house when he got out of prison, and serving as a confidante – in an effort to get close enough to obtain material that she could share with the police.

She started wearing a wire in 2013, and ultimately recorded hundreds of hours of conversations with her brother.

Willem Holleeder's lawyers, Sander Janssen and Robert Malewicz, criticised the timing of the book's publication. Willem Holleeder has been back in the maximum-security prison in Vught since December 2014, but he has appeared regularly at pre-trial hearings.

"It's not very favourable for any criminal case to have a book like this come out during the proceedings," Janssen said by telephone. "You never know if a witness will tell you something because he or she knows about it, or because he or she read it in a book."

As for Willem Holleeder, he reacted to the book with a brief statement for the panel of judges. "I have not terrorised my family," he said. "If this book had not been about me, I would have been as shocked as everybody else is. What Astrid said is not the truth."

Van Hout, the co-conspirator turned foe, once called Willem Holleeder "Judas", which inspired the title of the bestseller. But today, its author says she feels it is she who betrayed her brother.

She said that she "hates" herself for turning against her brother, and that, in spite of everything, she still loves him. She said she knew, however, that it was necessary to speak out, "to end the problem for everyone else".

New York Times