Bride of the Fae Duke by Lisette Marshall

Six wives. Six deaths. Can a humble housemaid break the curse?

The half-fae Duke of Locke is cursed to never find love… or so everyone says. But Nellie Finch does not believe in magic. As far as she’s concerned, that leaves only one explanation for the death of His Grace’s last six wives: he killed them himself.
It is therefore unpleasant surprise when, out of nowhere, the duke proposes to her.
Marrying this cold and unpleasant nobleman is the last thing Nellie wants. But his money can save her little sister, and Locke is damnably convincing about the arrangement. All he needs is an heir, and apart from the, well, necessary duties, she won’t have to see him at all. She should be able to survive that, shouldn’t she?
But when she begins falling for her mysterious husband, Nellie needs to figure out how to break the curse that killed six women before her… or be the next to die.