I read book and I loved it. It is as you said very bittersweet and it raises some good philosophical questions. The concept itself is very interesting and I liked how the POV switched from Henry to Clare. I haven't watch the movie because it looks like they made it very cheesy and diluted the story down a lot. Generally adaptations suck so I wasn't interested in watching it. If I'm bored and I see it on TV or something, I'll watch it.