Disappointing! I went into this book with the hope that it would be some kind of gothic mystery horror, but this was... nothing of the sort.  To begin with, right from the get-go my first issue with the book is the writing style; it's a lot of tell but not much show, which makes it feel like it was written for middle schoolers, even though I know that it is listed as being for adults.
The main pitfall of this book is that it definitely tries to bite off more than it can chew, which becomes apparent early on when it seems like every chapter is from the POV of a new character.  The constant POV changes means that not only do all of the characters have no depth to them, but that you will hear the exact same point being talked about over and over again... Even the few characters that do have a backstory are not intriguing - the only things we learn about them are things that would be important to know for the plot! And not only that, but as I said, you will have to read a lot of the same descriptions at least three times if not more. There's definitely a lot of hand-holding going on with this book.  
There's no need to speculate about anything or try to figure out the motives of certain characters because the book just tells you. And keeps telling you. And makes sure to circle it and highlight it and get big ol' signs spelling it out for you in case you missed it the first time. 
It's almost insulting how little faith this book has in the reader, especially since all this over-explanation only comes at the expense of the actual story.  I really could not pin down what this book was trying to go for tonally.  As I said, I went into this expecting some kind of gothic mystery horror, but it is not living up to any kind of genre descriptions, really. At the beginning of the book, when everything hasn't already been explained to hell and back, and there's still a bit of an air of mystery and wonder surrounding the train and the Wastelands, there are a few moment that I genuinely liked - there was even one scene that did briefly live up to my expectation for horror and spooked me a bit.  But of course, the writing almost immediately assures us that it's fine and everything's chill. Bummer. I would've liked for there to be at least some tension, but this book is obsessed with presenting an issue and then almost immediately either explaining exactly what it is or how to fix it.
Which brings me to another point - which is that this book is entirely too long for what it is.  There is absolutely no reason why this book should be 400+ pages. Period. End of story. Seriously, hardly anything of note happens in this book.  Actually interesting scenes are few and far between, and padded with a whole lot of nothing in between.  I guess you could argue that all that padding was meant for the purpose of exploring all of the plot threads going on here... but then you'd be wrong, because everything stays just as surface level as they were when they were first introduced at the beginning of the story.   Sure, we get a lot of scenes where the characters *talk* about whatever they're on that train for, but as far as any developments actually being made, you have to wait til the climax of the book, when the author tries to cram every story thread into a few chapters and resolve them all at once. It's frustrating, because a more experienced author definitely could've written all this (and better) within 300 pages or less. Emphasis on the less.  
And of course, the ending of this book is all neatly wrapped up with a bow and everybody's just fine with the things that happened to them and there's really no consequences whatsoever and everybody's happy and it's chill and blah blah blah the end.  But the most egregious part of all this is that the book literally ends with the epilogue saying What was the point of all that you ask? Well I don't know either!  WHAT!? You mean I sat through all of that for..... UGH. 
What a time waster.  Seriously disappointed with this book. So much squandered potential.