The FreeUse nature of this book has me biased against it. To me, FreeUse means "slut wife" and there's not much drama attached to reading about sluts having sex, unless the husband doesn't know or approve and that puts their relationship at stake. There's nothing exciting about reading about a prostitute having sex with her thousandth man.
For me, I see the rush of this couple into expanding on their lifestyle choice, well, more her choice than his, and it appears to be introducing drama and conflict into the story.
“That what goes on between the legs and what goes on between the ears are two very different things.” He nodded toward the stairs. “What goes on up there doesn’t affect what goes on in here,” he said, tapping his temple. “Your wife loves you, and nothing anybody else does to her changes that. If I’d been able to realise that with Grace, maybe we’d still be seeing each other.”
...
“Are you okay?” I whispered.
“Rob!” She gave a little shake of the head. “I’m fine. I don’t need your concern…” She slid her legs apart. “I just need your cock.”
To me, Suzy can love Rob as much as she wants, but it has to be felt and reciprocated by the husband too. I think that's the only "fault" of this book. The quotes above, combined with little verbalization of their love, makes me mildly skeptical about the viability of the relationship and wary of Suzy's motivations. Perhaps that's the point of this story leading into the third book in the series? (Note, you may not get the same feeling from this book, as it's not overt nor obvious. could be me picking up on things that aren't there because of the amount of cheating wife stories I've been reading lately)