Captain's Fury by Jim Butcher

In this book Tavi is masquerading as Captain Rufus Scipio, and his successes against the Canim have made him more political enemies than allies. But when he discovers that some of his suspicions about his parentage (that he's the First Lord's grandson) are confirmed and that his mother has been pretending to be his Aunt Isana his entire life, he's faced with a crisis of trust. The fate of the realm depends on his ability to take up a new mantel as Princeps. I really enjoyed this book. While I liked the idea of Gaius Sextus having to do without his furies, those scenes weren't as interesting as Tavi's. These books are not the most epic high fantasy I've ever read, but the series is well-plotted and very enjoyable.