And I think Paula Hawkins' The Girl on the Train is the perfect book to read while commuting, for reasons that are sort of obvious.
Rachel gets the train to and from work every day, and every day the train stops at red lights in the same place - opposite a house that is home to a beautiful young couple. Rachel has given them names, and careers, and lives vicariously through her imagined version of their perfect lives. And then one day, things are not so perfect. The woman in Rachel's perfect couple goes missing, and the man is under suspicion, and Rachel thinks she knows something about what happened.
The unreliable narrator is in vogue right now, but Hawkins injects a welcome shot of something different into Rachel. She's definitely an unreliable narrator, but Rachel wants more than anything to be reliable. She knows people don't trust her, and she knows she's give them no reason to, but she also knows that she's not cried wolf before about something like this. Accompanying Rachel as she struggles to work out what she knows about the missing woman, and how she knows it, is fascinating. Hawkins has created a character full to the brim with faults, but despite that Rachel is sympathetic and likeable, and I rooted for her all the way through.