By Jeffrey A. Trachtenberg

Alex Berenson has spent much of his career as an investigative business reporter and a writer of spy thrillers. Now his skepticism of how governments are handling the Covid-19 crisis has put him at the center of a controversy over the pandemic and Amazon.com Inc.'s market power.

Mr. Berenson said Thursday on Twitter that a booklet he wrote about the pandemic was rejected by Kindle Direct Publishing, Amazon's self-publishing arm. Titled "Unreported Truths About Covid-19 and Lockdowns," it argues that estimates about the deadliness of the disease have been overstated and that lockdowns have been counterproductive.

Tesla Inc. Chief Executive Elon Musk criticized Amazon's decision in a tweet that said, "This is insane@JeffBezos."

Amazon later said in a statement that "the book was removed in error."

On Friday, the self-published booklet was No. 2 on Amazon's Kindle Store bestseller list.

Mr. Berenson's views on Covid-19 put him out of step with most policy makers and public-health experts, who believe lockdowns have been necessary to slow the spread of the disease and prevent hospitals from being overrun.

Mr. Berenson said that toward the end of March he became increasingly skeptical about the models used to forecast the number of hospitalizations linked to Covid-19. He then used Twitter to raise questions as to whether a national lockdown was necessary to prevent the health-care system from collapsing. "When I said the system wasn't collapsing and the models were wrong, people hated that," Mr. Berenson said in an interview.

His views gained traction on conservative media, including through his appearances on Fox News. His Twitter following exploded. Critics pushed back on his claims. Fox News and The Wall Street Journal's parent, News Corp, share common ownership.

"This is a deadly virus that affects the most vulnerable, and anything that minimizes that is ignoring the facts," said Dr. Nancy Nielsen, a senior associate dean for health policy at the University at Buffalo's Jacobs School of Medicine and Biomedical Sciences and a former president of the American Medical Association, in an interview Friday.

"She's right," said Mr. Berenson. "The question is, what should be the correct response?"

Mr. Berenson, 47 years old, began his journalism career in 1994 at the Denver Post, where he was a general business reporter. He left in late 1996 and joined TheStreet.com, the online financial website. In 1999, he joined the New York Times, where he covered the pharmaceutical industry and was an investigative reporter.

His first spy novel, "The Faithful Spy," was published in 2006. The book did well in hardcover, but took off as a paperback in 2008, he said. Two years later he left the Times to become a full-time novelist. He has now published 12 spy novels, with a new book expected to be released in 2021, Mr. Berenson said.

In his new booklet, he accuses the media of failing to be skeptical of forecasts about Covid-19, saying, "media outlets seemed committed to painting as bleak a picture of coronavirus as possible."

This controversy isn't Mr. Berenson's first on the national stage. Last year he published the book "Tell Your Children: The Truth About Marijuana, Mental Illness, and Violence," which linked the use of marijuana to psychosis and violence. "It's far more dangerous than people understand, and some have suffered greatly," Mr. Berenson said.

An open letter signed by dozens of scholars and clinicians criticized the book and urged "policy makers and the public to rely on scientific evidence, not flawed pop science and ideological polemics, in formulating their opinions about marijuana legalization."

A Rolling Stone magazine headline asked, "Is Alex Berenson Trolling Us With His Anti-Weed Book?" The story's author wrote that Mr. Berenson had provided "distorted, dog-whistle conclusions."

Mr. Berenson said he is currently working on two additional booklets about Covid-19 that he expects to self-publish as separate titles. The first will be about the national lockdown, and how and where the virus spreads. The second booklet will focus on what the future could look like.

Mr. Berenson said he asked Amazon for assurance that he will be able to publish those titles on its self-publishing platform. He said Amazon told him they would decide on a title-by-title basis. A spokeswoman for Amazon said that all submissions are reviewed to ensure they comply with content guidelines.

Write to Jeffrey A. Trachtenberg at jeffrey.trachtenberg@wsj.com