The Girl on the Train starts out pretty confusing at first since you get to see the story unfold from several perspectives and it is not always clear of what is real and fantasy. While I think this could have been done better it does add to the suspense since you pretty much doubt every main character in the film at one point or another.
The red herrings are done superbly since even for me a fully fledged fan of the thriller genre did not see some plot twists coming. Mind you there aren't that much of them and it is possible to predict most events but still the main one came at a point that turned everything you saw around and made the film totally worth it. There are some graphical depictions of vomit and such I could have done without. (I don't know what this obsession it is these days with film and TV makers to show that in all it's glory. It's one of those things that you easily could imply without actually showing. I mean for god's sake nothing wrong with leaving some movie magic right?) Yet there is a definite purpose to it and quite brilliant I might add so in this case it is something I am willing to overlook. Just don't eat while you are watching this film and you will be fine.
What really sells this film is the good acting of the entire cast. They make everything believable. Even when at times you are asked to suspend disbelief too many times. Now do realize that these are very typical in mystery and thriller land and that is something you will have to accept or you will never be able to like this genre. For some reason this film is called the poor man's Gone Girl. I don't see the connection. Apart from a few similarities the movies couldn't be more different. The Girl on the Train is far more grounded in realism than Gone Girl is and in my opinion works better as drama since in this one you actually care for some of the characters.
Overall I wasn't bored a single second although I did struggle in the beginning a little following the story. But that was only for five minutes or so and then the film plays out rather conventional. In short this is very much worth your time.