Mark Zuckerberg was 'explicitly dismissive' of Facebook COO Sheryl Sandberg's comments in early meetings about building a giant ad business, a new book says

• Tension between Mark Zuckerberg and Sheryl Sandberg made employees "Mark people" or "Sheryl people."
• The revelation comes from a new book, "An Ugly Truth: Inside Facebook's Battle for Domination."
• One worker was reportedly "puzzled about the public portrayal of them as amazing partners."
• See more stories on Insider's business page.

An early wedge between Facebook's leaders had ripple effects across the company, leading to most senior employees being unofficially designated either "Mark people" or "Sheryl people," a new book says.

Facebook CEO Mark Zuckerberg "wasn't all that interested in the details" of the ad business COO Sheryl Sandberg was leading for Facebook and "brushed off" her requests for meetings, more staff, and a bigger budget, according to an advance copy of "An Ugly Truth: Inside Facebook's Battle for Domination" that Insider reviewed.

One employee on Facebook's business side told the book's authors, Sheera Frenkel and Cecilia Kang, that Zuckerberg was "explicitly dismissive" of Sandberg's remarks in some meetings.

"I've been consistently puzzled about the public portrayal of them as amazing partners," the employee said in the book.

Zuckerberg and Sandberg met at a Christmas party in 2007. Several conversations later, they agreed to have Sandberg join Facebook to focus on expanding advertising on the platform, which Zuckerberg had typically ignored in favor of expanding technological features, the book says.

"She had thought, from his interest during their courtship dinners, that Zuckerberg was committed to strengthening the business and that he would be actively supportive of her role," the book says of Sandberg. "As the weeks went by, though, it became apparent that she would have to fight to capture his attention."

The wedge between the company's leaders extended to their respective teams, separating tech and non-tech employees.

"There was mutual distrust and annoyance," the book says. "Engineers looked down on the 'marketing guys,' and the business managers struggled to get into meetings with Zuckerberg's teams."

Tensions between the leaders led Sandberg to enlist Donald Graham, then a member of the company's board of directors, to "lobby Zuckerberg for more resources on her behalf," according to the book.

"His priority of growth was miles above advertising, revenue, and profits," Graham told the book's authors. "It became my job to call him after every time Sheryl called and try to convince him about the importance of advertising, and not to change his priorities, but to help him move a little."

Facebook spokesperson Dani Lever denied any early tension between Zuckerberg and Sandberg.

"This book tells a false narrative based on selective interviews, many from disgruntled individuals, and cherry-picked facts," Lever told Insider in a statement. "The fault lines that the authors depict between Mark and Sheryl and the people who work with them do not exist. All of Mark's direct reports work closely with Sheryl and hers with Mark. Sheryl's role at the company has not changed."