Facebook’s two most powerful and visible executives, CEO Mark Zuckerberg and COO Sheryl Sandberg, have “drifted apart” over the handling of policy matters, according to a book extract published in The New York Times on Thursday.

Cecilia Kang and Sheera Frankel, authors of the book An Ugly Truth: Inside Facebook’s Battle for Domination, due to be published next week, collected testimonies from former and current Facebook employees at all levels of the business. 

They claim that in spite of appearances — the fact that, seemingly, nothing about Zuckerberg and Sandberg’s partnership has changed, that they meet twice every week, and that they remain personally and professionally close according to people who know them — behind closed doors things aren’t as they once were.

Zuckerberg is “less swayed by Ms. Sandberg’s view” than he was when he first hired her to do the bits of his job he found “boring” 13 years ago, the extract says. Sneakers2090 ,The Facebook CEO was also “critical of her handling of public relations” relating to election interference and the Cambridge Analytica scandal, the extract says.

Facebook spokeswoman Dani Lever strongly pushed back against the claims made in the book, saying that judging from the extracts the company had seen so far, the authors tell “a false narrative based on selective interviews, many from disgruntled individuals, and cherry-picked facts.”

“The fault lines that the authors depict between Mark and Sheryl and the people who work with them do not exist,” Lever said. “All of Mark’s direct reports work closely with Sheryl and hers with Mark. Sheryl’s role at the company has not changed. The excerpts are typical of attacks on women leaders — denying their power, dismissing their competence, and marginalizing their roles and relationships.”

The authors declined to comment on Facebook’s response to their published extract.

They detail how Sandberg first came to work with Zuckerberg and how he at first delegated political matters to her due to her experience in Washington. But as Donald Trump, who Sandberg “did not like,” became president, Zuckerberg increasingly disagreed with her and increasingly made important politics-related decisions himself, the authors say.

Facebook denied that Sandberg was any less involved with policy issues than she’d been previously. “Both Mark and Sheryl have spent more time on policy issues — and hired more senior members to the team, including Nick Clegg who reports to Sheryl,” said Lever. “These areas demanded more time, attention and focus, which both Mark and Sheryl have given them.”

One such point that did require more time, attention and focus was the circulation on Facebook of a doctored video that purported to show House Speaker Nancy Pelosi slurring her words. After a drawn-out consideration process, Zuckerberg made the decision not to take the video down, in spite of the fact that Sandberg thought “there was a good argument to take the video down under rules against disinformation.” (Lever defended this decision, saying: “it’s easy to criticize the process, but there isn’t a playbook for making policy decisions that make everyone happy, particularly when attempting to apply standards consistently).

The authors claim this tested the relationship between Zuckerberg and Sandberg, the latter of whom had actively fostered a good relationship with Pelosi. When Sandberg was later challenged over this decision and the company’s other issues involving privacy and regulation in an interview with Katie Couric, she defended the company calmly and adamantly. “She later told aides that inside, she was burning with humiliation,” the extract said.