I know it's terrible of me to say this, but I did not like the book.
*waits for outraged screaming to subside*
I thought it was melodramatic, full of gratuitous sex scenes, and slightly disgusting at times. It was, however, written well enough and emotively enough that I cried like a baby several times during the book, and expect to do so several more during the movie. I hated the last scene of the book; I loved the last scene of the book. The book made me intensely sad.
*The 40ish-year-old man having sex with an 18-year-old? Even if she does grow up to become his wife, that's still disgusting to me, especially when he time-travels back to his wife in the present day and notices how she's older/less attractive now — it's basically like cheating on her with an 18-year-old, even if it is her at age 18.
I'm not saying it isn't well-written; I'm not saying it didn't deserve to be made into a movie. I'm saying it made me sad, and I disliked parts of it (e.g. the constant sex and disgusting factor) enough not to want to read it again.
But I think the movie actually looks better than the book, so far. It looks like it deals more with the wife's life without her husband and her anger/issues, which to me would be much more profound issues.
Plus, Eric Bana plays the husband. Mm-mmm.