The last fiction book I read (over a decade ago) was Harry Potter and the Deathly Hallows and the reason I read it is because I had watched all the previous Harry Potter films and wanted to know what happens but the movie didn't exist yet at the time. I was hooked and there was literally no other option. I'm sure this effect worked very well in J.K. Rowling's favor.
Some people claim that they prefer fiction in book format because they can fill in the gaps and imagine the worlds and characters however they like... But personally, I prefer getting as much information as possible; visual information is part of it. If I had to choose between watching a film in color or black-and-white, I'd choose color for the same reason... With black and white, I could let my mind wander and assume that the person's clothing is made of gold yarn but I'd rather not as it mostly distracts from the story and those aren't details that interest me.
When I consume fiction, I'm looking for narratives, external perspectives, messages, lessons, principles and insights in a format that is as objective as possible. In book format, there's too much that comes from me, I end up projecting my pre-existing biases into the story and it doesn't feel as satisfying or mind-expanding.