(Disclaimer: I don't normally read Romance. I'm in a Reader's Advisory class in grad school and we have an assignment where we have to read books in a genre that is outside our comfort zone. For me, that's Romance and it's definitely impacted my reading of this novel.)
There is absolutely nothing wrong with this, but Romance is seriously just not for me. This was good, fluffy fun (which I am certainly NOT opposed to), but MacLean liked to use the same words/expressions over and over again (I swear, if I had to read about "turgid nipples" or "lips of her sex" or "plundering of the mouth" one more time...) I was also frustrated by Gabriel's anger at Callie's exploits because if she were caught it would ruin her reputation (and thus his sister's), yet in the next moment he would be sexing her which I would imagine would be ruin her reputation far more thoroughly than being caught drinking scotch in a tavern.
What I did really like were the relationships between the women, especially between Callie, her sister Marianna and Gabriel's sister Julianna. I also appreciated that Gabriel's ex-mistress Nastasia defied expectations (she could so easily have fallen into a sort of "mean girl" trope and she doesn't.)
The sexy bits were good, but as I mentioned above, I found they began to feel repetitive. I was lukewarm about the central romance though I enjoyed the characters separately, and even together (their banter is quite fun at times.) This book isn't reinventing the wheel, but MacLean pulls off the tropes she's utilizing quite well -- they just happen to be tropes that I'm not into reading which obviously is no fault of hers.
Would I recommend it? To Historical Romance fans, most definitely. It has fun characters and I felt transported to 1800s England.