All The Missing Girls by Megan Miranda, 2016
Nic, her brother Daniel, her ex-boyfriend Tyler, her best friend Corinne (the missing girl), and Corinne’s boyfriend Jackson
The Summary (from Goodreads):
It’s been ten years since Nicolette Farrell left her rural hometown after her best friend, Corinne, disappeared from Cooley Ridge without a trace. Back again to tie up loose ends and care for her ailing father, Nic is soon plunged into a shocking drama that reawakens Corinne’s case and breaks open old wounds long since stitched.
The decade-old investigation focused on Nic, her brother Daniel, boyfriend Tyler, and Corinne’s boyfriend Jackson. Since then, only Nic has left Cooley Ridge. Daniel and his wife, Laura, are expecting a baby; Jackson works at the town bar; Tyler is dating Annaleise Carter, Nic’s younger neighbor and the group’s alibi the night Corinne disappeared. Then, within days of Nic’s return, Annaleise goes missing.
Told backward—Day 15 to Day 1—from the time Annaleise goes missing, Nic works to unravel the truth about her younger neighbor’s disappearance, revealing shocking truths about her friends, her family, and what really happened to Corinne that night ten years ago.