There is a lot that writers of different persuasions can learn from each other despite their differences. Books and movies both have advantages and disadvantages when we’re talking about story.
Starting with the most obvious, the time taken to watch a movie is (usually) much less than that necessary to read the book of the same story, and a movie gives the watcher more aural and visual information which a reader must imagine. The writer, on the other hand, has much more scope to insert information which it’s impossible to include in a commercial length movie.
Commercial considerations and the particular skills of writers, publishers, screenwriters, directors, actors and editors of each version will shape the final book and movie. Whether the book or the movie of a story is better often hangs on personal preference and those commercial decisions.
A writer of books will always need to read and analyse as many stories as possible to continue learning and keep up-to-date with their craft. However, analysing movies to study story is efficient and effective as anyone who has watched Casablanca over the course of a day with Robert McKee can attest.
I highly recommend Alexandra Sokoloff’s website Screenwriting Tricks for Authors to anyone wanting to learn more.