This post is a comparison of the movie Something Borrowed versus the book by Emily Griffin.
I found the book to be a million times better than the movie. In the movie, as a viewer you immediately side with Rachel and not at all with Darcy. Darcy is seen as a manipulative bitch and bad friend. In the book, the reader is truly torn between who is in the wrong. The book is more thought provoking and interesting, while the movie is straightforward. I think by reading it you get more out of the story and understand more. That way, you're not just watching a chick flick but thinking about your morals.
I really liked the casting that they did though, I think that Darcy was chosen perfectly. And Ethan I think? I liked him a lot too. The rest of the characters were easily likable too.
Another major difference between the book and the movie is that Rachel's friend (I think her name starts with a C or something... the one who dislikes Darcy and is supportive of her) is nonexistent. Her part of the supportive friend is replaced by Ethan, and it's a nice twist of the story. I actually enjoyed that difference More than the book. I think it flowed better and put some drama into the story.
The movie didn't get very good reviews, which I can understand. If you're interested in the movie, I would suggest reading the book at some point to truly understand the story.