I confess that I have not yet read any steampunk, although from the outside it seems like something I would like. Do you have any links to share?

Here’s one of my favorite examples:
Prudencia placed the box down, tiring of this juvenile discourse. “You shall allow me to pass and fulfill my commerce with the proprietor of this establishment, or you shall be dispatched henceforth into a lavage of mire in yon boulevard.”
The men stood silent. “What the heck did she just say,” asked the large one.

She tries really hard

But trying to speak like someone from another era. . .if you aren’t going to research how they spoke in pretty serious depth, I wouldn’t even bother. Clean, clear voice with only as much slang in dialog as you absolutely can’t get away from (and you can get much farther away from slang than most writers think) works far better than a stab at the voice of an era you haven’t totally researched to the point of exhaustion. And nobody researches the voice of an era to that point but a historian specializing in that particular era.

You notice that Andrew doesn’t need a formal tone. “he cried, stepping closer,” works partly because it’s timeless. The impact is straight and true.

The clue is to plug into the real details and the real people speaking and acting in your novel. Because no matter what the era, no matter how long ago or how far away, people are people. And that’s what matters.

Oh, and just to add to Andrew’s clarification (because I know just a smidge about his book), he doesn’t have to worry too much about historical details, since this is steampunk/alternate history, and I’m certain he’s already hammered out the timeline and details.

Here’s a question for you, Victoria: how formal a register (in speech and narration) do you feel ideal in a historical?

Interesting interpretations on all of it…
I think one small thing that could clarify it is that he’s not stepping closer to intimidate her…he’s positioning himself to swipe that pistol back. Maybe I need to change it to “he cried, eying the trembling pistol.” or something like that. And they certainly don’t love one another…their marriage (earlier that day) was only a bargain to solidify his power (because of her supposedly “pure” bloodline which was bunk) and her wish to, well, become someone important with power.

What changes everything is that not only does the Duke launch an ill-fated coup with ends almost before it begins, he then tries to sneak away from it in a cowardly fashion, which she just can’t tolerate.

The premise is more complicated than what you stated. It’s definitely about ambition, and the bloody path it leaves, but the man who really is brave and noble is right there in the room with them, but because he’s not titled, she never sees him (until now).

Definitely gives me a lot to think about!