Happy Anniversary: An utterly unputdownable psychological thriller with a shocking twist

Three years ago, the narrator's husband was murdered on the same date she lost her high school best friend in a car crash. She has since rebuilt her life, working as a make-up artist and maintaining close friendships, though the anniversary of these two deaths remains difficult. On this particular anniversary, the narrator finds an unexpected gift box in her handbag with her name written across the lid. Inside is a message stating that someone is attempting to sabotage her life and will not stop until she is destroyed. The message is written in a code that her deceased best friend invented before she died. The novel follows the narrator as she confronts this mysterious threat and attempts to uncover who is behind it.