So this book basically focuses on the girl on a train - Rachel - who witnesses something from said train one day, which she then gets herself involved in and a who-dunnit style story takes place. It's also a 'what happened' story as Rachel is an alcoholic and regularly blacks out, and she desperately tries to remember the events of one particular night. Each chapter focuses on one character, told from their perspective, swapping between Rachel, Megan and Anna. 
 I did like this book. I felt compelled to keep reading, to find out what happened, who did it, etc. However, this book has the rare honour of me liking reading the book without liking one single character in it. The biggest character (bum-tish), Rachel, went from being sympathetic to dropping the 'sym' and being just plain pathetic. And kind of insane. I was cringing hard at literally everything she did, drunk or sober. Anna and Megan were both dislikeable in their own ways, as was every male character. So that did put me off the book a bit, as every decision Rachel made was terrible and literally the whole story could have been avoided if she'd just minded her own business. 
 That being said, I did want to keep reading this book from as soon as I started. I really liked the way it was told through the 3 different characters, getting their differing perspectives of the same event or filling in the blanks from someone else's story.