I am sure at some point in your life you have heard these words: “You shouldn’t watch the movie before you read the book!” Let’s discuss this statement.
The Nature of Books and Movies
Books and movies are two different mediums of storytelling. At it’s core, both authors and movie directors aspire to impact their audience with a story and its adjacent themes. The difference, of course, is that an author tells a story solely through words, while moviemakers tell a story primarily through images and accompanying dialogue.
The beauty of movie adaptations is that scenery and the appearance of characters, which were once words on a page, can be vividly seen in a film. But books have images too, right? It’s just that these images are visible in your mind, not on a screen.
There’s that popular saying, “A picture is worth a thousand words.” It’s true, but pictures always portray every specific detail while language can leave them out—language can be general or specific. Let me explain: if there is a picture of an oak tree, for instance, the viewer of the picture sees every detail of that image. Nothing can be left out. A viewer cannot look at the picture and change anything about it. Words, on the other hand, can address both sides of the equation. You can read “There was a tree” or “There was a twisted oak tree with roots like snakes stretching from its base.” Both sentences speak of a tree, but the first is general while the second is specific.

This brings us to another important point: how the reader or viewer interacts with their respective medium. When one reads a book, the author does not present the world as fully-described images. Though the painter intricately styles every leaf of a tree, the author paints with the broad strokes of words. This is something to be thankful for: if an author described every leaf of a tree, books would be unbearably long and, to the average reader, quite boring.
Now, when you and I read the phrase, “There was a tree,” we picture our own go-to image of a tree. This tree becomes the reader’s tree. True, the author told us to make it, but we painted it in our mind. We created it—or at least transplanted the image from a tree we’ve seen. As in my example of a specific tree image, sometimes the author creates most of the image. The reader still fills in the small details in this case, but the significant ones are creations of the author.
Authors, to whatever extent they deem important, outline the world or setting of a story while readers, with our mental images, fill in the rest. Regardless of the author involvement, the reader gets to participate in creating the visuals of a story. This construction of images effectively makes the reader a co-creator of the book’s scenery under the tutelage of the author.

Movies, on the other hand, are pre-set and unalterable. Once a movie premieres, no one can really change anything about it. And this is not a bad thing necessarily: a photographer or animator can present a much more beautiful tree than I could ever paint in my own mind. But it does mean that viewing movies is an inherently passive act, while reading is intrinsically active and participatory. In a sense, every book is a film—a fully immersive film where the reader is the producer, director, and set designer following the directions of the script writer, the author.
Issues with Adapting Books into Movies
When a book is adapted into a movie, two very different storytelling mediums collide. Or more accurately, the images that the words of a book evoke are transferred into the thousands of different pictures that make up a movie. Put another way, the makers of the film adaption interpret the book as they read it, just like readers. When we see a movie adaption, we see the filmmakers’ collated representations of what they themselves envisioned while reading the book.
This is what causes a common reaction to movie adaptions: “It was different than I imagined it would be.” Well, of course! When reading, both you and the filmmakers interpreted the book in your own way, but the movie version only reflects the filmmakers’ vision. And this isn’t always a bad thing.
For Peter Jackson’s film adaption of The Fellowship of the Ring, I have heard some people say that the filmmakers imagine the book better than they did as a reader. But this is not commonly the case. Usually, we prefer the creations of our own imaginations to the creations of another, because our own personalized creations mean more to us.
Of course, some may dislike The Fellowship of the Ring‘s film adaption because it left out important people or events (*cough* Tom Bombadil). But, for sake of simplicity, I am assuming that filmmakers do not add or detract from anything the author wrote. Discussing those often grievous changes is for another time.
Why Reading Before Watching Is Best
Now back to the question at hand: should one always read the book before watching the movie adaption? In my opinion, yes.
Here’s why: when you watch a movie and then read its source book, the movie’s images and other senses—landscapes, character appearances, character voices—are the ones we use to create the world, not our own spontaneous and original images. Back to the tree example, when the author says, “There was a tree,” you picture the movie’s tree instead of your own tree. The moviemaker’s interpretation of the author’s words become you the reader’s interpretation; when this happens, readers lose the opportunity to co-create the world for themselves.

Objection 1:
Are any images actually original? So then why is using the film’s image of a tree worse than pulling some random image from my head that I may have taken from somewhere else?
True, there is not much difference between the two options on the surface. But when you read the book—assuming they are identical besides the medium—and all you see are images of the movie, then there is little point to reading the book. It would make reading a book a far more passive experience. It can be active only if you can interact with the bare language, attaching your own images that you take from your own experience, not the experience of the filmmakers.
Objection 2:
Can’t someone read a book after watching the movie and just be very careful to create their own images?
I suppose this is possible, but only if you have an admirable amount of determination! It would save you the difficulty if you read the book first. But you may find yourself in a situation where, for instance, you have watched The Lord of the Rings films but have not read the books. If encountering this, I recommend that, while you read the books, to consider them as entirely separate and distinct from the films. This may not work perfectly, but I think it would help. And I don’t, of course, recommend this because the films are bad, but because I want you to interact with the wonderful books to your full potential!

A usual complaint with movie adaptions is that they often change important things from the book. Reading the book first helps you know the source material so you don’t confuse yourself! But as I’ve mentioned, maintaining the active creative process that every reader gets to take part in—creating a world with the author—is something far too great to pass up, even for the most legendary of film adaptions.
If you’d like to see some additional reasons, check out ‘5 Reasons Why Books Are Better Than the Movie Adaptions‘!