This is a real treat, a wonderful performance of a very enjoyable book.
Set in the world of Ellen Kushner's Swordspoint and The Privilege of the Sword, it's about forty or fifty years after Privilege. Katherine is Duchess Tremontaine, and Theron, Alec's posthumous son from his very late marriage to Sofia, now a physician and a Doctor of the University, is her heir presumptive.
He's also young, romantic, a poet, and an eternal student, flitting from one field of study to another, currently studying rhetoric. His heart broken (most recently) by the artist Isolde, who painted him for a year and then was done with him, he meets the dynamic young magister, Doctor of History Basil St. Cloud.