I will say first that the author is an excellent writer. If you are seeking historical erotica this would absolutely and wonderfully fit the bill.
However (for me) this story sadly lacked the depth and development that I seek in romances. The sex came first and foremost with no true emotional connection between the charaacters until much later in the story. They basically married because they had sex.
I also felt the heroine was by far too accepting and eager to do unusual things to be believable.
Although I certainly don't mind graphic sex, I prefer for it to be portrayed within the context of a loving relationship. Otherwise I really don't enjoy it. This is just my personal preference.