Then You Were Gone - Lauren Strasnick

In the tradition of 13 Reasons Why, a suspenseful and heart-wrenching novel from the author of Nothing Like You and Her and Me and You.
Two years ago, Adrienne's best friend walked out of her life. One week ago, she left Adrienne a desperate, muffled voicemail. Adrienne never called back.
Now Dakota is missing. She left behind a string of broken hearts, a flurry of rumors, and a suicide note.
Adrienne can't stop obsessing over what might have happened if she'd answered Dakota's call. And she's increasingly convinced that Dakota must still be alive.
Maybe finding and saving Dakota is the only way Adrienne can save herself.
Or maybe it's too late for them both.