The Shadow & the King by Emma Elizabeth

Lunette has never failed a contract. As one of the most sought-after vampire assassins in Ichorna, she knows what she’s doing when she accepts a contract to take out the minotaur king of Delkos. It’s not her job to ask questions, but when faced with her target, she wonders if she should be asking anyway.
Basilious tries to be a good king to his people, but his advisors have been pressuring him to secure an heir for the kingdom. He always hoped to find real love and partnership, but the reality of an arranged marriage or single parenthood looms. As the day he must announce his decision approaches, the last thing he expects is to imprint on a would-be assassin.

This spicy novelette is full of swoony romance and a touch of court intrigue.