Two Wicked Courts

Una and her sister grew up being told wondrous and terrifying stories of the Fae, unearthly beings who can help or harm. The older they get, the less they believe, but before they grow too old, they try one last time to summon the beings. Unlike every time before, it works, but they do not meet helpful Fae, and are instead taken and trapped in the Fae realm.
Suddenly thrust into servitude and an eternal war between two rival courts, surrounded by magic and deadly court intrigue, Una decides she'll do whatever it takes for her and her sister to survive. While learning to navigate the unpredictable whims of the princes she serves, she gains unimpeded access to rumors and secrets: a currency more precious than gold.
But when the opportunity for liberation and vengeance arises, she seizes it, even if it means placing her fate in the hands of the Unseelie Court: an infamous faction of Fae renowned for their cruelty.