In high school and college composition class, students are asked to perform various writing exercises. Write something describing emotions without using the first person, for example, or write about a supernatural experience using only scientific terms.
This felt like the writers were told "give us a love story with minimal plot or characterization". We don't know who these women are. We don't understand what they're doing. We know they are "time agents" on opposite sides of the "time war" and we have no idea what that means. We see what they are doing but doesn't make sense, there is no purpose other than "it will help our side win"
Now you could say that, well, that's the point. War doesn't HAVE a purpose, it's often senseless. But that's not the point, because we don't understand it. So much time is spent explaining what the agents are doing, but for all we know, they could be dreaming, or watching other people, or participating in a creative writing class.
And, forgive me for being snide, but when I read a book about two people falling in love, I want to know a little more about them. To me, characters make or break a book, and the whole time I had no idea why I should care in the least about these two. They're lonely. Sure. Got it. Why them? Why fall in love with the other? We're given superficial reasons (I don't relate to the others) but no hook. Honestly, the only reason I kept reading was to see if the end would make any sense. And in my opinion, it did not.
Two stars for creativity, nothing for poor characterization, plot, and execution.