You mentionning mental images while reading reminds me something I found quite interesting a 3-4 years ago.
Ever read the book ''perfume'' ? I had to read it when I was in secondary 5 (11th grade a think) . It's the story of this guy who has this incredible sense of smell, and in fact the whole novel is based around that idea. The narrator describes everything through the sense of smell, and so if the main character enters a room, it won't say ''the walls were white'' but it will instead say ''the walls had the odor of rotten cheese in them''.
Now, a year after me and all my friends had read the book, they made a movie out of it. What was interesting was that every friend that saw the movie said that it was almost exactly how they had envisioned it. Myself included.
In other words, this very peculiar manner of describing things in the book had projected the very same images in our minds. Which is radically different from the usual, where everybody reads a book, imagines it totally differently, goes to see the movie and find it to not be like they imagined it.
Although I have never found an answer of why this is the case.