A new book shed exclusive details about Prince Charles and Princess Diana’s marriage. Although the royal couple’s nuptials were dubbed the "wedding of the century," Charles said after he proposed to Diana that he was hoping he would "learn to love" her.

The new biography, titled, "Prince Charles: The Passions and Paradoxes of an Improbable Life," was written by author Sally Bedell Smith and was scheduled to be released Tuesday.

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Smith, an American historian who specializes in writing biographies about leaders worldwide, said Charles and Diana had 12 dates from the summer of 1980 up until their engagement in February 1981. She said Charles was reportedly taken aback when Diana accepted the proposal but figured everything could turn out well for them.

"He was obviously anguished, and he said, 'She was someone I could learn to love,'" Smith told People Magazine. "He looked to his grandparents, which wasn’t a love match at the outset and thought, 'If they can do it and build a good marriage then I can do it too.'"

Diana, who was rumored to have had a few affairs during her marriage with Charles, perhaps didn’t have enough time to know Charles entirely, Smith said.

"I was stunned when I combed over the chronology they had only been together 12 times [before their engagement]," Smith said. "After they got engaged, he went away for six weeks. He was dutifully plunging ahead with his schedule, and she wanted him to be around and available and support her."

Smith also noted Diana did not have the easiest childhood, and it was her past experiences that later took a toll on her as she rose to fame.

"I learned how traumatic her childhood was and how scarred she was by her parents' divorce," Smith said. "Her bulimic episodes began when she was a teenager and under stress."

Smith continued, "She couldn’t have accomplished what she did without becoming a princess, but becoming a princess and world celebrity was one of the worst things for her personally."

In contrast, Smith indicated Prince William’s current wife, Duchess Catherine, was way more prepared and polished for her role as a princess than Diana ever was.

"If she had had Kate’s confidence and solid upbringing and nurturing family and academic success – all the things that have helped Kate integrate so seamlessly," she said.

Last month, newly surfaced letters written by Diana to her personal secretary, Jane Parsons, revealed the Princess of Wales did not have a romantic honeymoon with Charles, according to Vanity Fair.

"The honeymoon was a perfect opportunity to catch up on sleep," Diana wrote Aug. 15, 1981, on the Royal Yacht Britannia.

Diana and Charles married in 1981, separated in 1992 and divorced in 1996. A year after their divorce, Diana died in a car crash in Paris in August 1997.