Beauty and the Goblin King by Lidiya Foxglove — book slip

For the past decade, the Goblin King has remained secluded in his caverns, offering a gold coin for each night a girl spends with him. Despite his fearsome appearance, the girls return unharmed and silent about their experiences.

When her family faces financial ruin, the protagonist's sister Clara sees an opportunity in the Goblin King's offer. Driven by curiosity and a desire to uncover the truth behind the Goblin King's curse, she ventures into his world.

As she unravels the mystery, she discovers a man haunted by a past misdeed, and together they might break the curse that binds him. But with a witch who doesn't play fair lurking nearby, their journey is fraught with danger and desire.

First in the Fairy Tale Heat series.