I had some thoughts about this that I originally wasn't sure I was going to share, but since the question has come up . . .
Sure Henry was a cool time-traveling guy. However, as a mom I have to say that I found it somewhat creepy that a 40-year old man, naked no less, was initiating a relationship with a 6-year-old girl and telling her everything was OK because they were going to be married in the future. I know that Henry did not consummate their relationship until Clare was 18, but it almost seemed like he was grooming her for that. (It's "our little secret," more or less.) It seemed to me that all of Henry's talk about determinism robbed Clare of her self-will. I mean, if she is going to be his wife and there is nothing that can change that, it easily follows that she must be in love with him. And yes, Clare did seduce Henry, but Henry could have continued to be the adult and resisted until they met in real time.
Now on the other hand, I also could not understand why Clare was so obsessed with having Henry's baby. She saw how badly time travel could turn out for Henry. Why would she risk that happening to her child? I also did not understand why Henry bothered having a vasectomy. He already knew that Alba was going to be born, so how could he think that a vasectomy would stop that?
Kay, I also found it interesting that Clare disregarded multiple warnings about Henry. But since she "knew" him from a little girl, it was easier to dismiss them.
Sara