I am impressed with C.S. Harris's ability to continue to weave a tale with characters she's explored thoroughly. I recently read a book by another author in a similar position (multiple books about the same characters), and Ms. Harris's work remains fresh and interesting to me, whereas the other author's does not now. Part of this reaction is Ms. Harris's believeable storyline, and obvious knowledge of the historic period.
I do see that she might be grasping a little; this novel contains more profanity and more crassness. I don't think she depicts her male protagonist (Sebastian St. Cyr) as sympathetically as she has in previous work. However, this change may be the result of intentional character development.
She also gets more into the vernacular of the period, which I find interesting but that might turn off other readers. I think this is a more technical manuscript in terms of vocabulary, but it's easy to follow and engaging nonetheless.
I enjoyed it, and look forward to the next novel in the series.