I was impressed at the thoroughness of the author's arguments and how well she constructed the story to illustrate her points, even better than her sermonizing. The slaves in the book were powerful people in their own right and in their own ways. I wasn't expecting that. I was expecting her to portray them as victimized children. But the book was way more subtle and complicated than that.
She calls out the southern slave owner who is a kind master who loves his servants, but is complicit in the system as much as the cruel plantation owner who treats his slaves worse than he treats his animals. She also calls out the self-righteous Northerner who professes to hate slavery, but does not see the slaves as people and equals.
I'm glad I finally read this!