I'm not sure what to make of this book ultimately. I love time travel books so I was excited to read this one. I don't know what I was expecting but it certainly wasn't what I got.Marina was an incredibly hard character to like. Actually, I really didn't like her throughout pretty much the whole book. Sure she had some growth towards the end, but it was too little, too late. The way she treated Finn and Luz...Just no... I just couldn't stand her. I also disliked James. He was unstable from the get go, and not the kind where I would have felt some kind of sympathy or compassion or pity. Anything to balance it out. The only likable characters were Finn and Luz. Without them I would have stopped reading this a long time ago. Finn was so sweet and caring and just such a great person. Sadly, Luz was only there during the beginning, so really Finn was the saving grace.I also didn't like how the story was set up. We kept getting flashbacks from Finn and Em about what had happened to them, but not once could I come up with how it all really went down. I couldn't connect the how of their situation had come about from what it was before, because as much as James was unstable I didn't think he was that stupid to have been manipulated like that, but I guess I was wrong. So what was the point of all the flashbacks? They don't even tell us how Em became such a badass. Nothing at all was explained till about the last 5% and by then I just didn't really care. It was also a very unsatisfying explanation and that ending was also a cop out.Throughout the book we are told that James = Time machine = Doomed World. Therefore, Em + Finn have to save the world by killing James. But it was never once explained HOW it all goes down. How James built the machine, how they started using it as a weapon, how that even worked really and why James let it all happen. This was, like I said before, all explained in the last 5% of the book. Too little too late.Let's talk about the time travel concept that was used here. I didn't get it. I mean theoretically when they explained it, I got it. But I just don't see how it could all actually work out. It seems as if every time they used the machine to go back in time it's as if you had reset time for a short period. Therefore time starts from the point in which you went back. If nothing significant changes in the amount of time that Time gives them before they get killed off, the future stays the same, but if it does change before that person gets taken by Time then it all resets from that point on? It's all just really strange and hard to follow, because I still can't comprehend how all that would work, with how much they actually change. This is also ties in with the silly ending. Silly because I just don't buy it. Young Finn died before young James did which means that with everything that we are being told Finn should stay dead, but instead James stays dead and Finn somehow gets to live? I don't get it! Why point that out specifically (Em and Finn were discussing this exactly before they confronted James), when you are not going to even follow through? It's not like I wanted Finn dead. He was the only character I truly liked, but I just can't accept that ending either.So yeah, this book by no means is unreadable, but there were just entirely too many things I didn't like in the end.