In a writing manual that the great Stephen King wrote, he talked about writers needing a toolbox for their chosen career. As an e-book writer, you will have a need of many of the various tools that King talked about (e.g. knowledge of proper grammar and punctuation, et al), but you will also need a few extras because you are targeting a new and specific breed of readers.

As a creator of Kindle e-books, you also need to have at least basic working knowledge of the following applications. Keep in mind that basic working knowledge means knowing beyond how to open and close files in these applications. You have to know how to create even just simple files with them and edit them as well whenever required.