The Girl on the Train is sure to be compared to Gone Girl--it, like Gillian Flynn's work, is a dark thriller featuring troubled/flawed characters, multiple narrators telling their stories asynchronously, and a plethora of red herrings.
Rachel Watson is the titular girl on the train. Looking out the window as she commutes from the suburbs to London every day, she has constructed an idyllic life for a couple she often sees from the train, a couple who happens to live just a few doors down from Rachel's ex-husband Tom and his new wife Anna. Then one day she sees the woman she has been watching--Rachel calls her Jess but we soon learn her name is actually Megan--kissing a man who is not her husband Jason (actual name: Scott). Rachel, an alcoholic who drinks to the point of blacking out and makes many bad decisions, decides to go to Jess/Jason's house the next day and confront Jess.
The morning after this outing, Rachel remembers nothing of what happened--but she has a head injury and senses that something very bad occurred. Then she sees a news story with a picture of the woman she recognizes as Jess, saying that Megan is missing. Rachel insinuates herself into the investigation, which eventually leads in an unexpected direction. I won't say more because I don't want to ruin the suspense.
I found The Girl on the Train entertaining, although I thought there were perhaps too many red herrings. Hawkins does a good job of making the three women--all of whom narrate sections of the book--quite distinct (I can imagine discussions of what actress should play each in the sure-to-happen movie); the men, unfortunately, are less well-developed. While all the characters are flawed (when the most sympathetic character is a therapist who sleeps with a patient, you know this is true), they are not as repulsive as the characters in Gone Girl. I guess that's not exactly an endorsement, but it does allow you to feel less dirty when you finish the book. I recommend the book for fans of the dark; for those who like their mysteries a bit more light-hearted, stay away!