The deal, worth US$2.2 billion, had been announced in November 2020 and would have brought together two of the five largest American publishers.

US District Court Judge Florence Pan, in her ruling, said the government had convincingly shown that the merger would “substantially” lessen competition “in the market for the US publishing rights to anticipated top-selling books”.

Pan said her full reasoning for the decision would be issued under seal, as it relied on confidential business information.

The Justice Department hailed the decision, which comes only a week before crucial midterm elections in which Democratic president Joe Biden has tried to paint his party as defending consumers’ interests.

The Justice Department under Biden has been more aggressive than his predecessors in attempting to block mergers, with mixed success so far.

“Today’s decision protects vital competition for books and is a victory for authors, readers, and the free exchange of ideas,” said assistant attorney general Jonathan Kanter in a statement.

With 10,000 employees worldwide and nearly 15,000 books published per year, Penguin Random House, a subsidiary of the German Bertelsmann Group, dominates the industry in the US.

Simon & Schuster, owned by Paramount, is the fourth largest of America’s “Big Five” publishing companies, which also include HarperCollins, Hachette Book Group USA and Macmillan Publishers.

Big-name writers on the roster at Simon & Schuster include Stephen King and Doris Kearns Goodwin, while Barack and Michelle Obama and John Grisham have books published by Penguin Random House.

It is also preparing to release Prince Harry’s memoir, in early 2023.

Neither company responded immediately to AFP requests for comment.

Prior to the US action against the takeover, the UK’s competition authority had also taken a close look at the merger, as both groups have British divisions. It issued a favourable opinion in May 2021.