I am one of those people that read the book before the movie. Usually, I see the movie before reading the book.
I can now understand how absences of scenes can prevent a person that has read in advance from fully enjoying the movie.
As for the movie, I felt like for the scenes that were selected, i.e. the Orphanage & Cave scenes, it did a great job! Overall, I was pleased with the movie, but definitely reccommend reading the book to fill in the awesome workings of J.K. Rowling!