Baron in Check by Sara Adrien

In Love and Chess, Every Move Counts.

Hermione “Hermy” Ellsworth was exiled to the countryside after a scandal threatened her reputation. Desperately seeking independence from an arranged marriage dictated by her late brother’s will, she must secure permission from her guardian—the very man who once held her heart.
Baron Gregory Stone “Greg”, known as the Black Knight for his unmatched skill in chess and feared presence in London’s social circles, finds himself entangled in Hermione’s plight. With two weeks to save her from a loveless union, he is unwilling to gamble—except when it comes to winning her love.
As a loyal friend of the Pearlers, featured in Sara Adrien’s acclaimed Infiltrating the Ton and Diamond Dynasty Series, Greg must play a high-stakes correspondence chess game with a villain who’s seeking to ruin his friends and Greg’s chances to pass a bill in parliament. Victory means Hermione’s freedom; defeat spells doom for her hopes of independence, Greg’s career, and his friends’ futures.