Nightspell

"Sent by her father, the king of Raellia, who is trying to forge an empire out of warring tribes, Darri arrives in Ghostland and discovers that her sister, whom she planned to rescue, may not want to leave this land where the dead mingle freely with the living."
"Sent by her father, the king of Raellia- who's trying to forge an empire out of warring tribes- Darri arrives in Ghostland and discovers that her sister, whom she planned to rescue, may not want to leave this land where the dead mingle freely with the living."@en
"Here be ghosts, the maps said, and that was all. In this haunted kingdom, ghosts linger--not just in the deepest forests or the darkest caverns, but alongside the living, as part of a twisted palace court that revels all night and sleeps through the daylight hours. Darri's sister was trapped here as a child. And now Darri has a chance to save her sister...if she agrees to a betrothal with the prince of the dead. But nothing is simple in this eerie kingdom--not her sister, who has changed beyond recognition; not her plan, which will be thrown off track almost at once; and not the undead prince, who seems more alive than anyone else. Can Darri's warrior heart withstand the most wrenching choice of all?"