The EPUB format is an open format that further allows you to convert it to any other common e-book format, including proprietary formats such as AZW3, KF8, and KFX, using the appropriate tools.
When you choose to export your masterpiece as EPUB, you will have the option of adding a Table of Contents and fine-tune it. When you're done, just download the resulting .epub file and use it in any way you want.
It's that simple: You seamlessly went from editing your masterpiece to casually downloading it as an EPUB file with a few clicks, without ever leaving Novelitist. As a matter of fact, you can download the EPUB version of this very guide, to see what we mean.
NOTE: the final look of your e-book (how your reader sees it) will be dictated by the device it is read on (as it should — your readers should choose what looks best to them): font family and size, paragraph styles, background color, and so on.