BlueGriffon is an open source WYSIWYG editor powered by Gecko, the rendering engine developed for Mozilla Firefox. One of a few derivatives of NVU, a now-discontinued HTML editor, BlueGriffon is the only actively developed NVU derivative that supports HTML5 as well as modern components of CSS.
If your goal is to write as little actual HTML as possible, then BlueGriffon is the tool you want. It’s a true drag-and-drop WYSIWYG website designer, and even includes a dual view option so you can see the code behind your design, in case you want to edit it or just learn from it.
It also supports the EPUB ebook format, so you don’t have to just publish to the web: you can provide your readers with a download of your content that they can take with them. Licensed under the MPL, GPL, and LGPL, a version of BlueGriffon is available for Linux, Windows, and Mac.