I don't have a copy of the actual book with me so I can't quote directly, but basically, he said that Rainier was very selfish especially when it came to inheritance. Princess Antoinette confessed to her son/Christian the time Princess Charlotte died that she and her children have no say in terms of who's getting what, and that Rainier wanted everything for him and his children. Another anecdote was about his (Christian's) second wedding -- apparently, Rainier forbade anyone from the Princely Family from attending the wedding. The only sympathetic person was, of course, Grace.
As for Caroline, he said that she denied him and his new wife of getting any seat in the Cathedral for Grace's funeral. He wanted to attend and pay his respects, especially since it was Grace who turned out to be the most loving and helpful member of his family, but Caroline apparently didn't want his presence at this time.
Christian was very gracious in acknowledging that Rainier was like a Father Figure to him and his sisters when they were growing up. He admitted his history of reckless behavior (inc. not doing well in school, issues with women and racing, etc), and noted that he did not have a healthy relationship with his mother. Rainier also has distanced himself especially since there was a time Princess Antoinette and her family were not allowed in Royal Events -- Antoinette was to be blamed: after all, she married Prince Rainier's main opposition!!!
Christian, all throughout the book, never mentioned about Grace turning against him. She was very helpful, insightful, and never judged him. Despite her very busy schedule, she always had time for him whenever he would call her for help or visit her at the palace unannounced.
Also, he said that when he first saw her (when the Palace Staff welcomed Grace in the Gallery of Hercules when she arrived for her wedding), he thought she was the most beautiful apparition he ever saw.
So, he's basically saying in the book that Grace was the most beautiful person in his life inside and out.