|Can words make you visualize this?|
Many, or perhaps most, readers form a inward impression of the characters and setting as we wend our way through a novel. The author has likely provided some detail which our mental image may adhere to but if you asked a half dozen readers for detailed descriptions of the main characters I suspect they would differ. The main character's most intimate thoughts and feelings are divulged for us to identify with. The image is personal to you.
When the story is transformed on film and watched in a theatre, the characters may not appear or even act in the way you envisioned. Those little individual features, the mannerisms and nuances may not reflect your expectation. The setting may bear little resemblance to the location and details you have created. Even the plot may diverge and follow the director's view of what was important, not yours. You may leave the theatre vaguely dissatisfied or even outraged.
But could all this have been avoided if you had deferred reading the novel?
In the theatre the story unfolds large and colourful on the screen. Perhaps it can be said that the movie version requires less effort from the audience than reading, even if the latter is sub-conscious effort. With the film version you don't need to create a mental image--it is provided for you. If the actors are skilled, their emotions are apparent. The authentic details in the setting are likely beyond your personal knowledge to even anticipate or envision. Does seeing the movie inspire you to read the book?
Books are often read in chunks. We've all had the occasional experience of staying up half the night to finish a spell-binding novel but often we ready a few chapters one day and another few the next or even several days later. A different kind of experience but one that unfolds at a slower pace. Is that like leaving to go to the restroom in the middle of a movie? Is the tension released as reality of the concession stand re-orients you to your real life?
When you've already seen the movie, Is it boring or meaningless when you read the novel and know how the story ends? Do you find yourself skipping the description and dialogue to get to the action? Does reading the book make you want to see the movie?
Movie first or book? It's your choice.