Wow! that was breathtaking. I have always found time travel fascinating and love reading books about it. Its about Em and Finn, you keep going back in time to try to stop the "doctor" from creating the time machine that destroys the world. 
 Its set in the past and future so it was really cool seeing the characters journeys; how they start off and how they evolve into the people they end up as. Especially, James. He is a sweet and nerdy guy and i was really intrigued to see how he ends up as the "doctor". It was also really interesting reading about him as the hero and the villain at the same time. 
 Em was a great character. Despite everything she's been through, she had so much spirit and was constantly fighting. Finn was just such a sweetheart and just made my heart swell. He was soo sweet and i felt his love for Marina even before when she was still in love with James. 
 I found it incredibly enjoyable and the twists and turns kept me hooked. I felt for Em when she was caught in the dilemma of whether to kill him or not. I m not sure i could have done it either. The ending was just so bittersweet and broke my heart. Since there is a sequel, i m looking forward to see how thing work cuz i have no idea whats going to happen after that ending. Its an amazing book and i would HIGHLY recommend it.