Storm Siren, by Mary Weber
This book starts out in a slave auction, where an arrogant young woman is being sold for the 14th time. Her merchant buyer immediately puts her up for resale after talking to her, but before the sale is complete her true talents are revealed and he's punished for his treatment of a young girl he's just purchased. And our heroine is bought by a very rich woman.
I enjoyed this book because it is well written and the heroine is interesting. So are the other characters. It is much better than the typical "warring kingdoms, girl who might save us" books.
The cover art is better than average as well. It captures the essence of the main character and is interesting to look at.