What I refer to here as "viewers" are the devices such as Kindle on which a person can read an electronic version of a book. A customer visits a website offering these types of books, pays the list price, and downloads the file to their viewer. Once this is done, the person can read the book at any time in basically the same way as a person who owns a printed and bound version of the same book.
     Any writer can get their book converted into the file type needed for the viewers. Of course, the first thing you need to do is write your story. Be sure to save the work in one of the widely available word processing software programs available on most computers. Although when you save the work, the program creates a file that can be opened by that particular program, the document might not be a type that can be uploaded to the service creating the electronic version. There is a chance the file must then be converted to another type. All of this will be explained by the service you use.
     These types of books are convenient for many people. They can easily carry more than one book on a long trip and there's no need for large amounts of shelf space in order to have a fairly large library. Other than the higher cost to purchase the viewer, the cost of each book is lower than if the person would buy a newly released novel in a printed and bound version. There are probably other reasons people prefer the high tech version of books, but since I don't own or use a viewer, I'm not aware of all of the existing reasons.
     Just as with any other publishing method, the basics are important. The writing process is still the same. The writer still needs to ensure the manuscript has been proofread and edited. Proper formatting is still required so that paragraphs and chapter breaks make reading smooth and easy. And, in the case of non-fiction, the information must be clear and accurate. What's being created is still a book even if it never has a cover or paper pages.
     Other than whether or not to create these types of books, the main decision an author has to make is when to release the product. Some authors will wait to create an electronic version of their book until months after the paper version has been available. This would be like a production company waiting for some period of time after a movie is being shown at a theater before releasing it on DVD. Other authors will make their work available for download within weeks of the printed version being published. Producing both within a short period of time will give people more options. There are some people who will only buy the electronic version and others who will only buy the printed version.
     Independent authors can expand their readership base buy creating both types of books. If someone reads and enjoys the book, they'll suggest it to other people. Having more than one version available caters to all of the people who might want to read the book.