Books and movies have different strengths and weaknesses. What works in one medium may very well not work in another. The pacing is also different - books can read at the pace of the reader; movies are watched in one sitting.

I have read the book but it was five years ago when it came out. Frankly, I wouldn't be the best person to ask how well the movie follows the book. I do think the movie captures the essence of the book quite well. The major themes of the book seem to all be there. I think it's only fair to judge the movie by how well it succeeds as a movie.

The movie (like the book) has the difficult task of setting up the grand finale while being entertaining in its own right. This it does brilliantly. New cast member Jim Broadbent is outstanding as the inherently decent but weak Horace Slughorn. The returning cast are also at the top of their game. Tom Felton as Draco Malfoy really shines here. He plays the anguished and conflicted Draco Malfoy for all it's worth. Draco seems to be a lot more sympathetic here than in the book. This is no doubt the filmmaker's intention; we'll have to wait to see how this plays out. Michael Gambon as Dumbledore is also great. The "three" effortlessly handle their roles. Radcliffe and Grint are especially good when "under the influence".

The only reservation I have about recommending this movie is that the previous five installments should be watched to get the full impact of the film. Otherwise only the Harry Potter fans who can't tolerate any alterations and/or omissions from the book have any issues with this fine film.