I would say the book is well-written and the story is, at times, very real. However, if you do not enjoy stories that will make you cry or upset you, this book is not for you.
**SPOILER ALERT--STOP READING NOW IF YOU INTEND TO READ THIS BOOK OR WATCH THE MOVIE**
The book follows the lives of two recent college graduates as it checks in with both of them on the same day just once a year. It's one of those two-good-friends-who-can't-seem-to-just-get-together kind of tales. However, usually you want to be rooting for them, but while the girl is pretty nice, the guy is a jerk. In all possible ways. He can't ever seem to do the right thing. Her flaws are mostly forgivable (though she does carry on an affair with a married man) and while the two do eventually get together later in life and try for the baby she has always hoped for, in the end, she dies. That's right, the character who has suffered enough and finally is about to have what she wants dies. Not the jerk who strung her along and fell down drunk half the book.
Now when I discussed the book with my friend she said, oh but he changed in the end because of her! Not really. Maybe the movie gives that impression more than the book, because as I told her, I think you leave more open to interpretation in cinematic art than in the written form because you have less ability to understand the character's innermost thoughts.
I do intend to watch the movie now, just to compare. I would say to avoid the book though unless you are someone who is able to really appreciate the writing rather than someone looking for a nice story.