What are the advantages and disadvantages of adapting a novel into a movie?

First of all, some words in the novel can't be expressed, but the picture is ok, the movie looks faster, and the effect looks good with music. If you remake the novel, it will enhance the popularity of the novel, but if the novel is well-known, the shooting will be expected, but if it is not well adapted, it may be controversial. Secondly, people who have read the novel will have fantasies about the characters, so once they are remake into movies, the characters will be more attractive. Many detailed words and pictures in the novel give people different feelings, and some people prefer words (I don't like to remake the novel into a movie, which is my personal opinion).