I've heard that the four medieval mysteries of which this is the last wasn't as successful as Penman's other books and no more are planned. Which I find a shame. I wasn't impressed with the first two books in the series. I thought the resolution and culprits predictable and Penman herself said in one author's note she wasn't completely comfortable at first dealing with completely fictional characters. The series grew on me though, and I think she grew in her skill in this genre.
I wouldn't put this up there with Ellis Peter's Brother Cadfael tales, never mind Eco's Name of the Rose. For that matter, no I don't think these rival Penman at her best. Her "The Sunne in Splendour" and "Here Be Dragons" are favorites of mine I'd rate five stars--these are definitely not in that league. But they are enjoyable and Justin de Quincy has become a friend I'm sorry to leave. Never mind it's a chance to spend time with her Eleanor of Aquitaine and John, the "Prince of Darkness" himself. I suspect that was one allure in writing this. I know having read her trilogy about Henry II and Eleanor I was drawn to reading this series became I didn't want to leave this world--and I'm sorry there'll be no more of them. Although it is a treat to see Justin and Durand inserted in her long historical fiction novel, "A King's Ransom" which I'm reading now.