FIRST LOOK: 'Secrets of the FBI' Reveals New Details on Marilyn Monroe Death, Vince Foster Suicide

Want to know more about how the FBI really works? How about never revealed secrets about celebrities, politicians, and criminals uncovered by agents during their investigations?

New York Times best-selling author and journalist Ronald Kessler writes about all of this and more in his explosive new book, “The Secrets of the FBI.”

Kessler even offers up some new tidbits on relations between then Attorney General Robert Kennedy and screen siren Marilyn Monroe.

“It never came out previously, but there was a teletype sent to headquarters from William Simon, who headed the Los Angeles field office, just after the August 5, 1962 death of Marilyn Monroe,” Kessler told FOX411 in an exclusive interview. “Simon was saying that he had lent his personal car to Bobby Kennedy to secretly see Marilyn just before her death.”

According to the book, many confidential files about this were destroyed after J. Edgar Hoover, the first director of the FBI, died in 1972. However, Simon’s children both confirmed that their father lent his white Lincoln convertible to Kennedy most weekends, and that one time Kennedy even left his Ray-Ban sunglasses in the glove compartment.

“As attorney general, Kennedy was entitled to be driven by an FBI security detail. The fact that he chose to use Simon’s personal car is consistent with William Simon’s report to headquarters that he lent his car to Kennedy for the purpose of clandestine meetings with Monroe,” the book continues. “Whether his last meeting with her, possibly to break up with her, may have contributed to her suicide is legitimate speculation.”

Kessler said that in those days, the FBI would keep potentially “embarrassing” information about any public official strictly confidential, yet it would often be used behind-the-scenes as blackmail material.

“Hoover would make sure that that public official knew that he knew. After that, that public official was afraid to say anything derogatory about Hoover or cut any of the FBI’s projects,” Kessler told us. “That’s why it never came out at the time.”

“Secrets of the FBI” also discloses fresh details surrounding the raid on Osama Bin Laden’s compound, the recent Russian spy swap, and precisely how the FBI eventually captured the mole in the U.S. intelligence community, Robert Hanssen. It even presents new FBI information pertaining to the 1993 suicide of former deputy White House counsel Vince Foster, and questions whether the then First Lady Hillary Clinton played an unintentional role.

“The Hillary material is pretty major and how she triggered the suicide of Vince Foster, according to the FBI agents who interviewed White House aides,” Kessler continued. “They reported that a week before Foster committed suicide, Hillary humiliated him in front of White House aides [during a meeting about a health care legislation she was proposing] and called him a small-town hick lawyer. After that, his friends and the aides reported that he was already depressed, but then he really went downhill after that and became totally withdrawn and, a week later committed suicide.”

Kessler writes that those present at the meeting told FBI agents that Clinton “violently disagreed with the legal objection Foster raised at the meeting” and thus “put him down really, really bad."

In response to a request for comment from Secretary of State Hillary Clinton for the book, Philippe Reines, senior advisor to the secretary and deputy assistant secretary of state, told Kessler that since she is focused on "the world's problems," her advisors "spare her from baseless distractions such as your fantastical accusations." As a result, "we will neither share them with her nor have comment for you," Reines said to the author.

Reigning FBI Director Robert Mueller, who was initially appointed by the Bush administration in 2001 and had his contract officially renewed for another term by Obama last week, also gave Kessler a rare interview for the book. After decades of covering the intricacies of the FBI, the author proclaims Mueller the most competent leader in the bureau’s history.

“He’s had the greatest positive influence on the FBI, overall. It’s turned into a very powerful tool against terrorism. When you get the details in the book on how it’s changed under him and why we haven’t been attacked since 9/11, you realize what an impact he’s had,” Kessler said. “William Sessions was one of the worst, because he abused his position and was eventually fired as a result. Lewis Freeh, despite a pretty good public image, really was a disaster, because he presided over some of the biggest fiascos that undermined investigations and undermined the credibility of the FBI.”

With “Secrets of the FBI” hitting shelves this week, Kessler is bracing for some backlash, particularly as he reveals unprecedented information on the TacOps, a super-secret division of the FBI that conducts more than four hundred court-authorized burglaries and covert entries each year to implant hidden bugging devices.

“I just had no idea that this operation is so involved and sophisticated and requires so much planning and creativity,” Kessler added. “There will be a lot of agents raising an eyebrow that they [FBI officials] gave me this. Some of them simply cannot believe that the FBI would go into this much detail about something that is so secret.”

Secrets of the FBI (Crown) goes on sale August 2, 2011. ($26)