I like anything from the Honorverse to varying degrees and I liked this one fairly well. I think the spy thriller description is a pretty accurate one for the most part.
The short stories,
Promised Land by Jane Lindskold (in The Service to the Sword) and
From the Highlands by Eric Flint (in Changer of Worlds) give some nice extra background info for this story. The first is about Ruth's mother and Prince Michael and how they first meet and the second has some background about Berry.
Also for folks that don't know
Crown of Slaves is available as part of the Baen Free Library...
http://www.webscription.net/p-92-crown-of-slaves.aspx