This was a pleasant surprise. Walker manages to create a future society that is believable and interesting (but which we unfortunately don't get to see much of), and the main plot, while some parts dragged and others were laden with lots of explaining (about the world, the mechanics of time travel, and so on), was, for the most part gripping and exciting. At times, I kind of got lost in all of the complications regarding the time travel, but managed to pull the threads together after a little bit of thought, which speaks to the author's explanations of these quirks and their consistency. The romance was a little too central for my liking (I always felt I wanted to get back to the time travel), but maybe that's just a feature of YA. It's clear that this book is shaping up to be a series, and I'm pretty interested in reading on; as mentioned before, this book sometimes got dragged down in trying to explain all the time traveling and such, and now that I have a pretty firm grasp on the rules of this world, it'd be neat to see some of the other adventures and the consequences of messing with some more timelines. The final confrontation was thrilling, and while I can't speak to the accuracy of the historical elements of the plot, they weren't distracting and mostly added to the plot. (view spoiler)[I also loved the whole Cyrists plot element, especially how it was thrown in casually before they made any reference to it being a fake religion. I wish the book had more elements of the warped timeline mentioned as "normal" in the "main timeline." (hide spoiler)] Recommended for those who like YA and/or light time travel!