If there is a movie version of a book, does that just mean that the front cover has a picture from the movie or is the story/text inside changed/different as well? 

For example, I recently read "The Reader".  I have not yet seen the movie but I read the copy of the book that has Kate Winselt's photo on the front, from the movie.  Would this be different from the book that does not have her pic on front? 

Another example is "My Sister's Keeper" by Jodi Picoult.  I read and loved that book a few yrs ago but now there is a movie version out and I see a new copy of the book out, with a photo from the movie on the cover.  If I read that book now, will it be the same exact one as I read a few yrs ago or will it be different to reflect the movie? 

Thank you for any info!

Unless the book says "adaptation" or something similar on the cover, it's the exact same book with a movie tie-in cover.

Sometimes, a book will be changed to reflect the changes that are made when a movie is made of a story, but as Britney noted above, those editions usually are noted as revised or updated or adapted on the front cover somewhere.  Much more often, the cover graphic is the only thing that changes, to try to cash in on the movie publicity to help sell the book.

And some of those get new ISBN numbers and some don't. 

Now with kid's books and movies, you have to be real careful.  The notice of adaptation can sometimes be inside.  There will also be several reading levels available, the classic, the revised, some easy readers, and some picture books.  Just look at how many forms The Polar Express came out in.