Roughly, what if Columbo was playing the Game of Thrones, and had a ninja's skillset* (not even a regular ninja, a ninja seemingly blessed by the god of ninjas). (The third in a series of 7 by Megan Whalen Turner, but the first I've read.)
Here's the Amazon link, although I enjoyed it in Libby.
*Now that I think about it, we see in the series that Columbo's an adept climber with great dart skills and knowledgeable about arcane poisons