This book was non-stop and had me guessing and second guessing on just about everything. This is the first book I've read by Cristin Terrill and she is a fantastic writer. This world she created, both timelines, and the characters that populate it are so vivid. Em and Marina live in two completely different worlds, and they also live 4 years apart. Em's job is to travel back 4 years to where Marina is and kill the man that is responsible for the horrible future that she currently inhabits. Sounds fairly cut and dry, but nothing is really as it seems in All Our Yesterdays. Em and Marina are both such interesting characters. Em is darker, her motivations stem from a gruesome world and desperate need to make it all right. Marina, on the surface, is a fairly typical teenage girl. Incredibly self centered and only really concerned about her best friend James and her desperate hope that he loves her the way she loves him. You'd think having these two characters are the main narrators for the book would be jarring, back and forth between such polar opposite personalities. And while it did take me a bit to get used to it, once I got into the story it really gelled together well. I had so many theories on what was really going on throughout the book. On one page I was certain it was one thing, but then by the next chapter I was convinced it was something completely different. This, to me, is the mark of fantastic storytelling. While I was reading, I was under the impression that this was a stand alone novel, and I was fairly satisfied with that. Although I didn't quite understand exactly what was going on at the very end of the book, I did feel like it fit in perfect with the rest of the story. Now I've learned that there is going to be a second book and I am definitely curious to see where Cristin Terrill is planning to take this. This is an awesome book, something a little different from what I usually read, and I'd definitely recommend it to anyone looking for fantastic storylines and well drawn characters. This one's a keeper!