The Girl on the Train, written by Paula Hawkins, is a gripping urban mystery fiction book set in London. The story revolves around Rachel Watson, a troubled woman who becomes entangled in a missing person investigation. As Rachel tries to piece together the events surrounding the disappearance, she becomes increasingly unreliable due to her alcohol addiction and memory lapses. The Girl on the Train is a suspenseful and atmospheric novel that explores themes of obsession, betrayal, and the unreliability of memory.