Apparently Katherine Kurtz had said from time to time that she would like to write more books in the Adept series, but I really think that Death of an Adept was a great spot to end the series.
Raeburne is back with plans for power that come out of the events of the first book, tieing a nice bow on the series. After christians, druids, and buddhists, we throw in Satanists. And we finally get the resolution of the Adam-Ximena romance (although it took me a while to get past her father's death in hospital, coming after being there for my own mother's death in hospital a little over a month ago. I was very prone to tears at that point).
Raebourne is trying to reestablish ties with the pictish thunder god. As a result, he brings in Taliere, a druid with ties to the events of Lammas Night (and allowing the authors to bring in one of the characters from the third book of the series, which otherwise was completely disconnected from the overall arc of the series). This leads to a grand confrontation with supernatural creatures, ghosts (both good and evil) and a life or death struggle during a satanic mass.
It's hard to evaluate this book on its own, since it is the conclusion of a series (while leaving the door cracked open for future books if they ever *do* write any). As a standalone book, I don't think it would work. But as the conclusion of the series, it ties everything up neatly and in a satisfying manner. I give it extra stars for that.