The book is certainly not for everyone. It's extremely adult, as many other reviewers have noted, while also dealing with some of the most grave issues scarring history. The story is not mainstream romance -- not even mainstream menage a trois romance. 
 The story starts out with the well known and much beloved trope, forced proximity, with a lovely twist (on a ship!) and goes from there to extremely adult adventures for the liberally minded. Janet Mullany pushes boundaries with her storytelling and her writing, and you should like very frank, very earthy details in your love scenes to fully enjoy what the author can offer. She doesn't shy away from what many other writers happily and readily gloss right over. 
 The book pairs two subjects you wouldn't think would work together: very kinky explorations along with a serious eye-opening look at the sugar trade on an island loosely based on Antigua about eight or ten years before the slave trade is abolished in England. (I cringed and my gut twisted while reading many of the passages involving slaves. Not pretty.) You wouldn't think those subjects would mesh at all, but in a weird way, they do. It's not as if modern people don't get up to serious mischief while the problems of the world continue to rage on right in our faces. However, at the heart of it, what holds the whole story together is a remarkable and easy-to-like heroine. All you need to know about her is this quote from early in the book which portrays her character perfectly: "Whenever she wished she had had the moral courage to starve... she was glad she had the good sense not to." 
 And, of course, Janet Mullany has an exquisite ability with words. Her voice is like rustling silk and you can read any of her work for the subtle beauty of her style alone. Her depth of knowledge of the time period is effortlessly conveyed in her writing.