Mary is cut from a different cloth to the other women in society - she wants a purpose beyond matrimony and motherhood. She is an endearing, ballsy, vulnerable and endlessly likeable. Her character's development was wonderful to watch, and felt totally plausible given the passage of time covered in the book.
Tre is struggling with an illness he finds shameful and keeping it, and many other things, secret. He is stoic, charming, commanding and gentle. I really enjoyed the dynamic that he had with Mary throughout the story, but I particularly enjoyed seeing how their relationship with each other developed over the span of the several years that the story covered.
The real touches of historical accuracy added depth to the story and were clearly very well researched. They helped me to completely immerse myself in the world that the author created.
The only reason I didn't give this book 5 stars is that it felt a little slow to start for me; to the point where I read the first 10% and then went off and read something else before revisiting the rest of the story.