The only thing that bothered me about this book (and then only slightly) was that the time travel was fade in/fade out and seemed to be completely random. There is one line in the last chapter that hints there may be a way to control it, but the reference is vague and fleeting. 
 That being said, the story drew me in quickly. I found myself attached to Eva, Mark, and Susan from the very beginning. I think I may have even been teary in the first chapter.