This book starts tense and doesn't let up for quite a while afterwards. A good portion of it feels like a thriller but eventually that does change, the tension is not kept up throughout the book. 

It is a strange story which is probably not quite whatever you imagined when you read the blurb. The time travel leads to twists and turns which I for one did not see coming but were clearly planned from the beginning. The desire to understand what was going on was the main thing that kept me turning the pages once the tension subsided somewhat, and as a consequence this is probably not a book I would choose to reread. 

Overall a book that is worth reading once, but I didn't develop any connection to the characters or love the plotline enough for it to achieve higher than 3.5 stars.