Having uploaded my manuscript to Kindle Direct Publishing (Amazon), I used the preview feature to see how it will look as an ebook. I found a few spacing and formatting problems, and I learned there's more to it than that.
For instance, these two paragraphs look like normal bits of narration in my manuscript, but, on an ebook reader, they look like brick walls. The monotony of the page might make a reader think my story was tedious. These two paragraphs will become four.
This is not the way writers are trained to think. According to my ever-handy copy of The Elements of Style, "The beginning of each paragraph is a signal that a new step in the development of the subject has been reached."
However, in the world of independent publishing, the writer becomes a book designer and learns visual composition has a logic all its own. While consciously reading the words, the reader subconsciously follows the shape of the text.
Book designers have done this for centuries, making decisions about margins, line-spacing, indentation, typeface, and other things, all to make the appearance of the page support the intent of the prose.
New printing press . . . new rules.