I saw this in a theater in '75. I was 16 or so. I liked it at the time. But I also read the book at some point in the '70's, and find it much more memorable than the movie. Susann's books were, at that time, considered trashy fiction. They wouldn't raise a single eyebrow today. But the movie, which I just watched again, wasn't much like I remembered. Props to Brenda Vacarro for her joie de vivre, and a little bit to David Janssen for his acting chops. I did like Alexis Smith in this one. But the rest of the cast seemed to just mail it in, even Kirk Douglas, who we all know was a phenomenal actor. Deborah Raffin has an excuse because of her age, and maybe she meant to play the ingenue that way, but, well, let's just say that I do not recommend this film.
Review of Once Is Not Enough
