noir fiction vs gothic romance

Is there a rule or convention or expectation that every installment in a series of novels has to be the same type of story? I mean what trope is the determining factor? As long as each book in the series has the same setting and mostly the same characters, does it matter if one volume leans more toward action and the hero's journey, and the next is a romance, and the third is a dystopic allegory, and the forth a war story?

I was told once by a beta reader that Curious Weather had "too much romance" for the type of book it was. This assessment, I must assume, was based on the fact that The Curse of Jacob Tracy was a weird western—a boy's adventure book, to be blunt—with no sex and only the barest allusion to romance.

So, naturally, I doubled down on the love story in Curious Weather because the whole point of that book was that it IS a romance, albeit a gothic one.

What are the tropes of the gothic romance? Well, Barbara Michaels is/was my favorite of the modern writers, and she did a batch of supernatural-flavored ones in the 80s, so I take her as my guide.

1. Told from the POV of the heroine, who's out of her usual milieu due to a family shake-up of some kind—or in the modern stories, a professional change.

2. The heroine's new milieu is hostile or threatening in some way, because of isolation, locals, or roommates—or all three.

3. There is at least one love interest, usually two. These two heroes are foils for each other; one seemingly, the other unsuitable in some way, both attractive and/or menacing by turns.

4. Usually the charming love interest turns out to be the villain.

5. There's a mystery afoot, or some deep dark secret.

6. The heroine's efforts to solve the mystery or uncover the secret lead her further into danger.

In many ways it's the same plot as a hard-boiled detective story, just with the gender roles reversed.

I'm pleased to say that Curious Weather alternately embraces and subverts all of these tropes, sometimes both, and you could make an argument that it brings in elements of the noir novel as well. As for the idea that there might be "too much" romance in a noir story... have you read any Mickey Spillane? or Robert B. Parker?