Some similarities are very important to understand the story even if it’s in book or movie form. Starting with the setting or city it’s involved in. They were both set up in the city of San Francisco. If one was set up in San Francisco and one in let’s say Denver then the setting of the whole story would be off. The one in Denver would have a colder feeling and people would be wearing coats and stuff from the one in San Francisco the feeling wouldn’t be as cold. So the setting similarity is very important to the story on a high level. Also the names of all the characters are similar. This is important because if the characters were named different and someone was trying to follow along then that would confuse that person. So say if the character is named Jake in one story and Spade in another then how you would know without having to look for extra details like features of the face. Also the title is the same. I know there is a movie called Satan Meets a Lady that is a version of the Maltese Falcon. A movie watcher wouldn’t know that the book is related to the movie without putting two and two together. The movies name is very important to the person comprising and just wanted to see the movie. I love book related of movies and it’s easier to find if they had the same name. Those are only just a few similarities of the book and movie there are a lot more. So all the similarities are really important, from weather it’s to understanding the book verses the movie or vice versa.
The differences in the movie from the novel are a big part of putting together the two stories. For instance Iva Archer to me was a bigger part of the book then she was in the movie. In the book she caused insufficient problems