That's not surprising. That's a normal trade when covering mediums. Sometimes it bothers me too much but normally I'm okay with it as long as the spirit is there.

Occasionally the medium switch makes the book better. Jurassic Park for example. The ending in the book is just bad and the author didn't do nearly enough to get me to care about the characters. The movie fixes all of this.

Though the book opening is better than the movie IMO.