I love the story and the film stuck mainly to it. The few deviations, however, seemed completely unnecessary. Why, for instance, was Gavroche the one who gave the letter to Valjean? Personally, I feel that Eponine’s death becomes that much more pitiful when she dies helping Marius get with Cosette than her dying trying to save Marius. Maybe that’s just me, I don’t know.
I can't say anything about the musical, but it's actually Gavroche that gives Valjean the letter in the book. When Éponine is shot in the barricade taking the bullet that is meant for Marius, she decides to give him Cosette's letter as she's dying. She wanted Marius to die in the barricade because if she couldn't have him, no one could have him and decided to give him the letter as she didn't want him to hate her in the afterlife.
I was surprised they didn't mention that Gavroche is Éponine's little brother.