I just finished listening to Changeling by Philippa Gregory book 1 of the Order of Darkness series, it was fabulous. Luca, a suspected changeling who had been given to the service of the church as a young man after his parents disappeared, is the inquirer, who travels across Europe exposing witches, poisoners, werewolves and other threats to the church.  Along the way Luca meets Isolde, a princess who has lost her title, lands and family who was forced into the service of the church. After Luca leads an inquisition at the Abbey Isolde runs, their lives and futures become entwined.

I just put book number two, Stormbringers on hold.  This is a fantastic series for teens and adults alike, especially those who enjoyed novels by Melina Marchetta, Cinda Williams Chima, and Megan Whalen Turner.