01/10/2014 09:30 am ET Updated Jan 25, 2014

Gabriel Sherman Defends His Roger Ailes Book From Fox News Attacks

Gabriel Sherman answered critics of his upcoming book about Fox News CEO Roger Ailes on Friday's "CBS This Morning."

The rollout for "The Loudest Voice In The Room" began this week, revealing stunning claims — including one allegation that Ailes once offered an employee a raise in exchange for sex.

Fox News has battled Sherman for months now, and aggressively pushed back against the book's claims this week. A Fox News spokesperson told The Huffington Post, “While we have not read the book, the only reality here is that Gabe was not provided any direct access to Roger Ailes and the book was never fact-checked with Fox News.”

On Friday, Sherman told CBS News' Charlie Rose and Norah O'Donnell that the book was factchecked.

"The book was factchecked with two professional factcheckers," the biographer said. "More than 2,000 hours went into vetting the manuscript."

"I reached out to Roger Ailes more than a dozen times for comment," Sherman added. "He ultimately decided not to, but that is revealing of his desire to control his story."

He also said he conducted more than 600 interviews with subjects, including Ailes' brother, for the book. He also looked at documents ranging from presidential memos to other archival research.

In the book, Sherman describes Ailes' rise to power from his childhood in Ohio to Republican strategist to Fox News chief. The book presents as a less-than-flattering portrait of Ailes as a man with an ugly temper, extreme political views that his boss Rupert Murdoch is skeptical of and many enemies among his colleagues, staffers and Murdoch's children.

Sherman said Friday that working on the book has been "a reporter's dream."

Roger Ailes is the "most powerful man in American that most Americans don't know and should know," Sherman said. "He is like Citizen Kane meets P.T. Barnum. He's a larger than life character, he controls the most powerful cable news network whose ratings surpass its rivals combined. When he puts something on air, it drives the agenda."