For folks who are looking for a good cross-reference between Peter Jackson's Movies and the Tolkien's books, I point you to The Encyclopedia of Arda which has just updated by adding a final installment of "Moviegoer's Guide" for RotK.
If you have any questions as to how the books and movies differ, or the specific details or significance of the alterations, it's a good place to start from. And it features convenient citations.
If you have any questions as to how the books and movies differ, or the specific details or significance of the alterations, it's a good place to start from. And it features convenient citations.