A new book has revealed the secrets of the tumultuous final year of John F Kennedy (JFK) and Jackie Kennedy’s marriage, including an alleged affair between JFK and Marilyn Monroe.

According to excerpts from the book In These Few Precious Days, Monroe called the First Lady to confess to the affair, telling her that JFK had agreed to leave his family for her.

Jackie Kennedy’s response was reportedly callous: “Marilyn, you’ll marry Jack, that’s great… And you’ll move into the White House and you’ll assume the responsibilities of First Lady, and I’ll move out and you’ll have all the problems.” The book claims that while Jackie Kennedy was generally tolerant of her husband’s infidelities, JFK’s relationship with Monroe caused her the most distress.

The book also alleges that JFK and Jackie Kennedy took regular amphetamine and steroid injections from a man referred to as “Dr Feelgood”.

The President is said to have received high-dosage shots around four times a week, despite concerns from doctors due to the cocktail of medication he was already taking for other health issues.

The First Lady is believed to have started receiving the injections herself after being warned against them by writer Gore Vidal, who had heard that “Max drove several people mad”.

In reality, Dr Feelgood was a physician called Max Jacobson.

Other details from the book include the revelation that JFK’s father, Joseph Kennedy, disapproved of Jackie Kennedy and even tried to cancel their wedding a few days before it took place.

The book also claims that Jackie Kennedy found solace in the company of her husband’s brother, Robert F Kennedy, after JFK’s assassination.

Author Christopher Andersen has written 34 books on famous figures, including Barack and Michelle Obama, Princess Diana, and Donald Trump.

In These Few Precious Days is based on interviews with over 100 people, including friends, family members, and White House staff.

Andersen describes the book as “the most personal, revealing, and emotional story I’ve ever written”.

The book is due to be published on 7 July.

The revelations about JFK and Jackie Kennedy’s marriage are likely to cause a stir, particularly the alleged affair with Marilyn Monroe.

Monroe and JFK are known to have had a close relationship, but the extent of their involvement has always been a matter of speculation.

Monroe sang “Happy Birthday” to JFK in an iconic performance just weeks before his death in November 1963.

The Kennedys remain one of the most fascinating political dynasties in US history, and their lives and loves continue to captivate the public imagination.

The new book offers fresh insights into the couple’s private life, including the darker aspects that were hidden behind the glamour and charm.

While JFK’s presidency is remembered for its optimism and idealism, the reality was far more complicated.