Stephen King Testifies That Merger Between Publishing Giants Would Hurt Writers.

The best-selling author Stephen King testified in a suit filed by the Justice Department to block Penguin Random House from buying Simon & Schuster, saying the merger of two of the country’s largest publishers would make it harder for writers to earn a living.

Mr. King testified as a witness for the government, which has filed a lawsuit in U.S. District Court for the District of Columbia aiming to stop the $2.18 billion acquisition.

The firms are among the largest of the so-called Big Five publishers, and part of an industry already reshaped by consolidation. Penguin Random House, which is owned by the German company Bertelsmann, is itself the result of a 2013 merger.

“Consolidation is bad for competition,” Mr. King said about why he agreed to testify.

Penguin Random House argues that the acquisition would benefit authors and readers. Its lawyers say that under the deal, Simon & Schuster’s authors would get access to Penguin Random House’s supply chain and distribution networks, and that the savings created by combining the two companies would translate into higher pay for authors.

Government lawyers used Mr. King’s testimony to illustrate their argument that consolidation in the publishing industry has hurt authors and the industry.

The testimony from the famed writer of titles including “It” and “Pet Sematary,” dressed in a gray suit and gray slip-on walking shoes, occasionally drew laughs from the audience in the courtroom’s gallery. Lawyers for Penguin Random House declined to cross-examine Mr. King after he spent roughly half an hour testifying.

Mr. King said that when he started in the publishing business in the mid-1970s, there were hundreds of imprints in the business, and he shopped his work around without an agent. The number of publishers has since dwindled, he said, as competing businesses were subsumed or collapsed.

With fewer imprints competing for business, advances have slowly dwindled, he continued, particularly for writers without a track record of sales.

Not that advances, the money paid to writers upfront based on anticipated earnings from royalties, were ever particularly generous for unknown writers. Mr. King said he received a combined $10,000 in advances for his first books, including “Carrie” and “The Shining.”

“It becomes tougher and tougher for writers to find enough money to live on,” he said.

Over the ensuing decades, Mr. King has penned numerous best sellers and earned a fortune from his books. That financial security, Mr. King said, enables him to publish books with smaller independent publishers, the kind emerging writers often go with to break into the publishing business.

He said that he accepted the smaller advances offered by independent publishers because he wanted to see those imprints survive.

“There comes a point,” he said, “if you’re very, very, very fortunate, that you can stop following your bank account and follow your heart.”