When movies are made into books there are bound to be differences, that is just the way it is. And I will admit, I have sat in the theater on opening weekend for every one of the Twilight movies (other than the last). I have also read each of the books, I just couldn’t help myself.
I have noted the differences between the movie and the book, and there are plenty of them. Here I will only mention a few.
There is no mention of a Cullen Family Crest in the book, but in the movie all of the Cullens are wearing some sort of crest as an accessory on their persons.
The field trip they take to the greenhouse does not exist in the book.
The scene where Edward takes Bella to his house, he is supposed to play her the lullaby. Instead, everyone is cooking for her. The lullaby is an integral part, because it leads up to him showing her the rest of the house thus leading into introducing her to rest of the family.
Charlie and Bella only eat at the diner a few times in the book, in the movie they eat there a lot.