You could get it online from Amazon. It is available if you check out the site. I have another book which contains more information about Rainier & Gisele Pascal - "Once Upon a Time: The Story of Princess Grace, Prince Rainier & their Family" by J. Randy Taraborrelli. It's also available from Amazon. The author indicates thta Princess Antoinette was very much opposed to the actress & that Rainier was unhappy by Gisele's dedication to an acting/movie career. He also cites a personal friend of Gisele's,Maureen Molnar,as enabling him to uncover information about the romance.
There was also Father Tucker who understood that this was not going to end in marriage. In his biography are letters which indicate that Father Tucker told her that it would not end in marriage. She is quoted as saying he was the one who sat her down and told her the truth. Father Tucker is also the one who helped arrange for Rainier to meet Grace.