The Queen’s Crown by Jennifer Anne Davis

Eighteen-year-old Princess Sabine Ludwig of Bakley thought her biggest problem was finding a man remotely interesting to dabble with while trying to fill her days with something other than knitting or drinking tea. But when her dear sister is brutally murdered in a foreign kingdom a week before she’s to be married, Sabine suddenly wishes for boring, ordinary days again.
Seeking retribution, Sabine decides to take her sister’s place and marry the mysterious king of Lynk. It’s the only way she can hunt down and find the killer. It’s the only way she can get revenge. When she finds the king far more appealing than she’d intended, it becomes difficult to keep her wits about her and remember why she’s there.
Thrown into a world of lies, power struggles, and seduction, Sabine must learn to navigate through the foreign kingdom’s dangerous court as she seeks her sister’s killer. The closer she gets to discovering who it is, the more she questions who she can trust—including herself.