Princess Diana struggled a lot during her tumultuous marriage to Prince Charles.

And what made it more difficult for the late royal to cope was the fact that she didn’t have really close friends in her life.

In the book “Diana: Case Solved,” royal writer Richard Kay said that he was one of the last people who spoke with the Princess of Wales just before she passed away. Princess Diana died on Aug. 31, 1997, following a fatal car crash in Paris.

Kay also said that even though Princess Diana seemed happy whenever she’s out in public, behind closed doors she was actually miserable. In order to fill the void of her empty social life, Prince William and Prince Harry’s mom turned to psychics and alternative healers.

Meanwhile, investigative journalist Dylan Howard and homicide detective Colin McLaren teamed up to write a book on Princess Diana. They said that Princess Diana barely knew Prince Charles, and this is one of the reasons why their marriage failed.

They also said that the Prince and Princess of Wales were ill-suited for each other that’s why their marriage was doomed from the start.

“The book’s authors promise you will learn of the covert diaries and recordings she made, logging the Windsor’s most intimate secrets and hidden scandals as a desperate kind of insurance policy,” the book information read.

“What’s more, the authors detail how the royals were not the only powerful enemies Diana made. Her ground-breaking campaigns against AIDS and landmines may have drawn admiration from the public, but they also drew enmity from powerful establishment figures including international arms dealers, the British and American governments and the MI6 and the CIA,” the information added.

“Diana: Case Solved – The Definite Account That Proves What Really Happened” is now available on Amazon. Hardcover and Kindle editions are available as well.

Prince Charles and Princess Diana
Prince Charles and Princess Diana are pictured at an official event during their first royal Australian tour 1983 in Newcastle, Australia. Patrick Riviere/Getty Images