Historical setting is confirmed as early 1800s, almost certainly prior to Victoria (1837). That gives it some context, sort of.
From my previous reading several decades ago I remembered the general plot and one of the major twists, but not much more, so this really is very close to a "new" read.
And now for a lot of spoilers.
The descriptions of the setting are superb, though I have to admit I'm sometimes a bit confused as to how much Mary can actually see in the dead of a rainy night.
I'll probably finish tonight, and then we'll see how I feel about Mary. Right now, I don't much care for her, and the rest of the characters are so icky that I don't care about any of them.