The Girl on the Train by Paula Hawkins

The Girl on the Train is a bestselling 2015 psychological thriller novel by Paula Hawkins about Rachel Watson, an unreliable narrator who becomes entangled in a missing person's case after witnessing something shocking from her daily commuter train, leading to a web of secrets, betrayals, and a search for the truth about her own past and the disappearance of a woman she'd been watching. The story, told from multiple perspectives, explores themes of alcoholism, obsession, and memory, and was adapted into a major motion picture