Among the richest of slave owners a psychopathic young girl breaks apart two families to get married to a man she doesn't like.
Seasoned by continuity errors and the most disgusting antisemitism since Dickens (pre-rewrite of Twist) for the chief's kiss. (there's an edition that edit the antisemitism out and if you want to protect the racist hate above the editor's, publisher's and right holder's freedom of speech you are a 20th century good German. A disclaimer that goes "aha just kidding with the antisemitism" is not good enough for a book written in 1950).

I can't get past how Sophy lies all the time, non-stop, except when she is just being dishonest or demeaning. Her rapist's mindset is in full display every other chapter: other people are not people but things to break to her will, and she knows what they want and will get them there, damn their consent and whatever the means. In the first half of the book she lies to every single character, kidnaps her rival, steals several times and more generally is a complete shit to everyone. She adds assault near the end of the book.
How does she get away with that? With plotholes and idiot balls! The author is a piece of shit and thinks that these behaviors are the best thing ever so literally every characters always trust and love Sophy to the point of torpedoing the whole book.

Maybe the worst disbelief-breaking event is when Sophy sells a pair of her own earring (she has not stolen them). But her maid does not know that and raise the alarm. Sophy immediately throws the maid under the bus by claiming that she sent them to be repaired and that her silly maid has forgotten, before being immediately privately confronted by her "love" interest with her lie. What does she do? She lies again, gaslit him and shit on his fiancee. It gets worse! A third character has immediately guessed that Sophy lied about the earrings and so goes to her rescue.
What does this third character says, 5 pages after catching up to Sophy's lies?

"Well, she ain’t one to tell fibs"

I shit you not.

It's Ripley except Ripley is treated as an angelic role model instead of the protagonist.

But it's a romance book, I am not supposed to look to closely at the plot, the setting, the character or the prose! What's important is the Romance!

What romance? Sophy does not even like her love interest! She is a complete ass to him every time, never express, show or think of him with any affection, never talks to him except to get something out of him or to demean him or his original fiancee, steals from him, and alienates him from his family and friends. On the other hand he is impressed by her lying and... her fortune.
(In the first chapter there's this gem: Cecilia's mother is pushing Cecilia to marry a richer older man and says "In short, Cecilia, [...] persons of our order do not marry only to please themselves.". Because marrying someone to vacuum their fortune is not selfish. Yeah.)

Sophy's fortune is a way for them to bond: they both are ready to burn hundred of pounds on horses, except the love interest is broke (for their definition of broke). That's several time the yearly pay of a lawyer, or enough to buy around 30 slaves. Because all of the main characters are slave owners. This is set in 1815 and they all own plantations and slaves in America, in Jamaica (see The Book Of night Women from Marlon James) and the Caribbean, in Malaysia... The US's slavery south has disappeared as a setting for romance because it is fucking disgusting and it's a summit of hypocrisy to be OK with regency high society.
The author aboslutely knows that given the detailed and accurate research that went in all the details of the setting.

I'm fucking done.