The Silent Patient by Alex Michaelides

 Nine months. Two weeks. Six days. That’s how long recovering addict Sophie’s been drug-free. Four months ago her best friend Mina died in what everyone believes was a drug deal gone wrong – a deal they think Sophie set up. Only Sophie knows the truth. She and Mina shared a secret, but there was no drug deal. Mina was deliberately murdered. Forced into rehab for a drug addiction she’d already beaten, Sophie’s finally out and on the trail of the killer. But can she track them down before they come for her? From the author of The Girls I’ve Been, soon to be a Netflix film starring Millie Bobby Brown