Something Borrowed: Emily Giffin. I hadn't seen the movie for awhile before I read the book which was perfect. From what I can remember they were fairly similar but I still loved the book. It was an easy read and strangely hard to put down.
Never judge a book by its movie. Something Borrowed is a fantastic book, and the movie completely altered the story line. And right after you read this, go pick up Something Blue and every other book by Emily Giffin.