The author of Bad Blood, one of the biggest books of the year, has left his day job.

John Carreyrou departed the Wall Street Journal this summer following the smash success of his book that chronicled the rise and fall of Silicon Valley sweetheart Elizabeth Holmes. Carreyrou exposed her blood-testing company Theranos as an apparent fraud before going on to write the book based off of his work.

Bad Blood has sold almost a million copies since it was released last year, Carreyrou told The Daily Beast during his first interview since leaving the Journal. The book is currently being made into a film starring Jennifer Lawrence as Holmes and inspired an avalanche of television shows, podcasts and documentaries.

Carreyrou said part of the reason he’s leaving the paper after 20 years is because of the Journal’s policy against paid speaking engagements.

“The Journal has a pretty blanket ban on its reporters taking money to speak publicly. If I were to do that or my colleagues do that it compromises the Journal. I respect the reasons for their policy but for me it meant leaving quite a bit of money on the table. I’m in pretty high demand due to the success of the book. I’m grateful for everything they’ve done for me.”

Paid speaking engagements are highly lucrative, with some journalists earning five-figure sums to give a speech to a company or organization.

The Journal said in a statement the policy exists to avoid the appearance of a conflict of interest: “The Journal has a deep commitment to the highest standards and ethics, including our guidelines around paid speaking engagements, because nothing is more important than the independence of our journalism. We never want our journalists to be in situations where those standards can be questioned, and neither do our readers.”

Carreyrou said just because he’s done with the Journal doesn’t mean he’s done with journalism.

“I’m not retiring,” he said. “I’d been there almost 20 years. It felt fitting to me. It has been a great place to me. I owe this recent string of success to the Journal but I needed a change. I want to keep writing non-fiction books for the second part of my career. That’s more my priority. I may find a home for my reporting in between books.”

Carreyrou has had discussions about joining several news publications, including The New York Times, according to a person familiar with the matter.

Carreyrou, who was born in France and has had reporting stints in Brussels, Paris and New York with the Journal, is a two-time Pulitzer Prize winner. In 2003, he shared a Pulitzer in Explanatory Reporting for a series of stories on corporate scandals; in 2015, he won a Pulitzer for Investigative Reporting for a series exposing fraud and abuse in Medicare that cost taxpayers billions of dollars.

His biggest story started in 2015 when he began chipping away at the glittering facade of Theranos and its charismatic young founder Holmes, who lured billions of dollars from investors with the promise of technology that could diagnose everything from cholesterol to HIV with one test of a small drop of blood.

A lot of journalists uncritically reported on the fantastic claims, until Carreyrou discovered that Theranos had cheated on tests, provided false data to patients, and that CEO Holmes allegedly lied to the company and its board.

After Carreyrou exposed the alleged fraud, the company folded. Holmes and her business partner, Ramesh “Sunny” Balwani, were subsequently charged with federal counts of fraud and conspiracy to commit fraud. Holmes and Balwani have both pleaded not guilty and are due to face trial next summer.

Carreyrou is the latest heavy hitter to depart the Journal. In May, Tom Wright left after co-authoring the best selling book Billion Dollar Whale about the Malaysian fugitive Jho Low, who partied with American celebrities by using the proceeds of what U.S. authorities say was a billion-dollar fraud. Wright on his Twitter account lists a contact for a paid-speaking agency.

Last week, Michael Rothfeld left the Journal for the Times after sharing a Pulitzer this year for a series of stories breaking wide open how President Donald Trump’s ex-lawyer Michael Cohen paid hush money to silence alleged mistresses of Trump in the run up to the 2016 election. Rothfeld will join the investigative unit on the Times’ metro desk.

Rothfeld has his own book due out in January with Journal colleague Joe Palazzolo tentatively titled The Fixers from Random House, which is expected to provide more details on the people who helped silence Karen MacDougal and Stormy Daniels for Trump, including the National Enquirer, and its parent company American Media.

—Maxwell Tani contributed reporting.