I'm not really sure how to rate this book. I'm giving it 4 stars when I compare to other similar themes but it leaves me rating confused. I'm honestly not sure what to think. This isn't a romance. This is a darker look at BDSM filling only the sexual needs of the persons involved. There's no emotional connection strengthened over the story between the two leads despite their long history. This is simply reviewing the contact between them when the dom calls and the sub's need to answer that call and how they fulfill that need in each other.
Sounding makes up a big chunk of the story. Made me cringe in a few places but that seems to be what the author wanted. Because of that, it was well written in seeming to get across what the author wanted. If you like a darker edge, it's a good read but don't expect a romantic hour while you read it. As others have mentioned, there are some distracting typos.