Let me start off by saying that I don't have any problem with the sexual content of this book. But some of the heavy breathing feels so overdone, it's just really silly. Some of the depictions of sex, like the description of when Johnson loses her virginity, are also a little creepy.
But more importantly, I was really hoping for a critical examination of the lives and work of Masters and Johnson. What I got was just overwrought gossip and all surface. To me, it felt like the book was mostly just a string of interviews the author conducted and had only started to make sense of. There is so much in here that does not require direct quoting and where the full quote was overkill, or only serves to repeat an idea that has already been drilled into our heads: Masters was distant, Johnson was independent, yeah, yeah, we got it. A bunch of random doctors and colleagues talking about the speculation going around the office about whether or not Masters and Johnson were having sex with each other. The narrative is driven by this collection of quotes, rather than the other way around. That only works if the people being quoted have anything interesting to say, which is rarely the case here. It's pretty vapid stuff - Wow, Bill Masters liked football! And he sometimes annoyed his friend (a former pro turned coach) with his chatter - not exactly riveting. You could condense this entire book to less than 100 pages without losing any substance and without really losing too many details, either.
Additionally, the dramas here aren't dramas, but the real dramas are ignored. For example, Johnson's looking up of an old boyfriend near the end of her life and feeling sad when she heard he'd died does not qualify as a drama in my book, but a normal human response. Yet the real dramas, such as the revelation that Johnson's initial employment was contingent on her having sex with Masters while he was still married and that she didn't want to, are dropped, only to be resolved by a short, seemingly unsubstantiated statement that she came to enjoy it eventually. WTF?
One of the parts of the story in which the author does attempt a more in-depth analysis is in the depiction of sexual mores in 20th century America - but even this is dumbed-down and uncritical. One of the more slightly interesting parts of the story was to consider how Masters and Johnson became a touchstone for feminists for a brief time - but even this is treated breezily and without any real tension.
I think good biography not only needs to reveal the details of people's lives, but to make sense of them. I really wish the author had treated this version as a draft and taken the time to provide an in-depth analysis and not avoided the real contradictions of Masters and Johnson's story.