Verisimilitude, or the appearance of being real, is the key to a successful story. It’s what allows one to get completely lost in a narrative and forget it’s a work of fiction. Verisimilitude doesn’t necessarily mean the story must represent the real world as we know it. A story set in a science fiction or fantasy world must also have verisimilitude, or in other words, everything must seem real and believable within the world of the story. While movies may appear to be the more “realistic” medium, I think it may be easier to achieve verisimilitude in books.
If you write a fictional story, it’ll look exactly the same on paper as a true story (words on a page), but a movie is noticeably different from real video footage or a documentary. We can almost always tell when someone is acting versus when they are being natural. Plus, the special effects, props, and sets are all fabricated to varying degrees of authenticity. On top of all that, if the acting is off, it will instantly take you out of the story, and you’ll realize it’s just a fictional movie.
With a book, however, the degree of authenticity comes down to the writer’s prose alone. Are they able to make the story believable through their voice, characters, and plot? If they write in a natural style (not too elevated language) then the story will feel real to the reader, even if there are extraordinary things like dragons and aliens. Yet movies, even with advanced CGI, aren’t able to make dragons that look 100% real.
I think the key to verisimilitude in fiction is naturalistic prose. Overly flowery language may sound beautiful and poetic, but it reminds the reader that the story was written, made up by an author, so it loses a sense of realism and takes you out of the story. Therefore, the language should be as natural as possible (which can vary depending on the age, background, time period, and location of the narrator in the story).
That said, the rare movies that do get it right, with amazing actors and special effects, are so viscerally powerful, even more so than books, because movies affect more senses (vision, sound, and music). If the verisimilitude is there, and you can see it visually, it feels more real than something simply imagined in your head. There’s a higher degree of difficulty in terms of budget and number of people involved, but when executed correctly, movies can match or supersede books in verisimilitude.
You can debate books versus movies, but the ultimate form of verisimilitude in fiction may be virtual reality. The technology isn’t quite there yet to create 100% realistic settings and characters, but given time, it will be in the future. VR games/movies/stories/experiences will be the most powerful form of storytelling. You could be in a fantasy realm with dragons and it will look and feel perfectly real. Instead of watching or reading a story, you will be inside the story, and the simulated world will be indistinguishable from the real world. It will require no imagination or suspension of disbelief. Virtual reality will feel like actual reality. Which leads to the question: Could we already be inside a virtual reality world?