for Endless by Kate Brian
Rory Miller didn't just fall in love with Tristan Parrish. She fell in love with the idea of forever. He was the one who told her the truth about her existence in Juniper Landing: that her mortal life is over, and she will now spend eternity on the island, helping others in limbo move on. But like Juniper Landing, a bright island with dark secrets, Tristan is too good to be true. The mysterious, heartbreakingly beautiful boy Rory thought she knew is responsible for unthinkable evil???sending good souls to the Shadowlands in order to get himself a second chance at life on Earth. He has already claimed Rory's friend Aaron and her own father, but when Tristan sends her sister, Darcy, to the Shadowlands, too, Rory decides to take matters into her own hands. She will do anything to save her family, even if it means going to hell and back.
Publisher description retrieved from Google Books.