I don't read a lot of chick-lit but I read Emily Giffin's Something Borrowed YEARS ago and they finally picked it up for a movie. Here's the trailer (which I think looks good). I love the actress that they chose for Rachel although I don't know how I feel about Kate Hudson being Darcy. She seems to have a decent grasp on her character's mean streak (Darcy is SO horrible in the book) but I dunno...guess I'll have to watch the movie to find out!
Rachel has always been the good girl- until her thirtieth birthday, when her longtime friend Darcy throws her a party. That night, after too many drinks, Rachel ends up in bed with Darcy's fiance. Rachel is completely horrified. She pretends it didn't happen, maybe it will all go away-and so will her feelings for this guy.
She prays for fate to intervene, but when she makes a choice she discovers that the lines between right and wrong are blurry, endings aren't always neat, and you have to risk all to win true happiness.