It may be that this book is the most difficult of all the Harry Potters to film, since there are several parallel and mostly separate story lines. The major problem was with the extensive omission of important plot details in favor of new and often confusing materials. One should tread very lightly when rewriting or editing JK Rowling. She mostly gets everything right.The complete redo of the climactic battle scene at the end of the book was just wrong, as was the addition of a scene where the death eaters invaded the Burrow.