Right.
It's going.
It's not bollocking toshfest material, it's just pffffffft, dunno. I'm 25% in, which is my cut-off, and I'm still not in it. If you were to ask me what it's about, (beyond Holy Grail goings-on) I couldn't tell you, because she's not started telling me yet. But I have a baaad premonition I'm going to be going "FFS Kate, did you even write a plan?"
It's not as badly written "he did this, then she did that" like a Philippa Gregory (which tbh, sometimes, is all you need) but it's definitely not "literary fiction" (under which broad banner I'd always placed Kate Mosse)
What has done it for me is:
Really, really badly written characters. (the tipping point came with the introduction of a female character who is clearly Going To Be Very Important having really really badly written sex - think Ken Collette meets Danielle Steel- lots of glistening sweat drops between fulsome heaving breasts- down Ken)
Stilted conversation when we are supposed to be thinking someone who can't speak fluent French is trying to, and someone who can't speak fluent English is trying to. (I can't stop seeing scenes from 'Allo 'Allo)
Ultimately, I like Holy Grail thrillers. (Use of English aside and shagging women 20 years younger than you aside, I've not got a bad thing to say about Dan Brown); I like historical fiction. And whilst knowing that the former is going to include some of the latter, KM's attempt at the double timeline, (and I can see there's going to be a clunky Lighthouse Witches/Dark ta-da thing) just seems contrived.
Her editor should have sat her down and said "show me your plan" and then crossed bits out.
Hey ho.