We started watching this recently, and have pretty much binged to catch up. I've read one of the books (the Cassie storyline) but not the other, but like everyone else I cannot for the life of me see why they combined the two. Why on earth didn't they do four episodes per book? Like, they'd still have been producing eight episodes, it just would have made more sense as two mini-series. It sort of seems like they've been doing that anyway, since the links between the two storylines are not exactly well drawn (yet, I suppose. But I can't see it).
Anyway, I don't mind the acting too much, though Tom Vaugn Lawlor (Frank Mackey) is basically doing Nidge - a pity as I've seen him in plays, and he's a good actor. The guy playing Daniel in the Cassie storyline is annoying (but I find him irritating in everything). I also hate the detective's boss - Lord Varys! - but seriously, laying it on thick with the swearing and inappropriate informality in an Irish lilt is bordering on the offensive (especially when it is clearly meant to be a contrast to Rob's buttoned-up Englishness).
What the hell is going on with the supernatural stuff? Have they forgotten about the academic having sex with his student on the altar, basted in red wine? WTF?
As I said, I haven't read the book about the killings in the woods, so here are my predictions: Rosalind is actually Sandra's daughter, and is involved in Katie's death in some way (some switch with the twin? maybe she meant to kill Jessica in order to escape from her caring responsibilities?).