Kate Mosse's thing is actually four things: There is the female protagonist(s); there is the south of France, Languedoc; there is the interweaving of the present and the past, two parallel story lines; and, there is the esoteric mystery, the innuendo of the supernatural. In these respects Sepulchre is very similar to the Labyrinth that I have read earlier.
I like the first characteristic, it's adding a nice variety to the novels I usually read. It's not a distinctive mark. There a lots of novels with female protagonists. Mosse manages, however, to not write for a stereotyped audience. In principle, anyone could enjoy her works.
I have no strong opinion with regard to the geographic location. Again, it adds some variety to the usual mix. Though it is not like I feel I could benefit from change in this particular aspect.
The two time lines and the parallel development of the plots I indeed like. The parallelism was much more pronounced in Labyrinth. In Sepulchre the link between the two time lines relies much more (actually: only) on the kinship of the protagonists. Hence, with respect to the stylistic devices Sepulchre is less interesting, less refined than Mosse's earlier novel.
Finally, I could certainly do without the supernatural. It's completely dispensable here. Some mystery, some unexplained events: yes. Ghosts, or supernatural entities: no.
In sum, still an (quite) enjoyable book. Though I am not sure whether or not I am going to read her next one…