This is one of those books that left me with mixed emotions. There are parts of it that I was very intrigued by (the time travel element, the different powers) and there were parts that were too predictable (the instant love and unbreakable bond...unbreakable except for the complication of a love triangle, of course....). Emerson has had a difficult life. She lost her parents and started seeing people who "aren't there". These visions have made her believe that she is crazy...a fact that led to a brief stint in an institution. Now that she's out, she's decided to stop her medication but that pesky side-effect of seeing dead people is back. 
 Emerson is a very interesting character; she's a bit of a contradiction though. She's spunky and cheeky in the beginning, a character who is seemingly looking to take control of her life. Off the meds and living with her brother and sister-in-law, Emerson is trying to move forward. But, enter Michael and she changes. It begins to feel like she just wants someone to take her by the hand and explain the world to her. Michael is a member of the Hourglass, an organization that we're not told too much about in the beginning, and he's got two reasons to be in Em's life. First, he wants to help her understand these visions and what they mean. Secondly, he needs her to accomplish a goal - to right a wrong that happened in the past. 
 Michael and Emerson have an immediate connection (there are literally sparks between them)...they are soul mates with a purpose, you could say. And here, in a nutshell, is where this story falls down for me. The romance should be epic but I couldn't feel the chemistry. I wanted to, but I couldn't...and I was saddened by that. The romance is such a large part of this book that I needed to feel the bond they were experiencing, to believe that it was real, but it just didn't happen for me. Now...later on we meet Kaleb and, although I couldn't quite understand the need for a love triangle, I could see some sparks there that intrigued me so much more! 
 The world that Michael introduces Emerson to is fascinating...full of possibilities but also filled with rules. Time travel is a complex thing and I love that the author puts in reference to negative matter and wormholes because it makes it all feel much more realistic. I enjoyed the second half of the book much more than the first as this topic came to play a larger role. There are definitely twists and turns here and some tense moments. There are also strong characters, some you're not sure you like, some you trust and some you just can't put your finger on. I really enjoyed the fact that they had different abilities and that, in this world, some of those powers are interdependent and stronger when merged. 
 There are many unanswered questions at the end of this book and lots more to explore in this world. Plus there's the possibility of Kaleb shaking things up in the romance department! All of this should make for some good reading in the sequel!