In the absence of a WYSIWYG editor in JavaFX WebView, the SHEF project provides a fine alternative. Click to enlarge the image below.
Aside from being to generate to/from EPUB, project templates are provided for creating new EPUB 3.0 and EPUB 2.0 books:
The structure of the app is modular and Mavenized:
One thing I will do is replace all Matisse GUI Builder forms with plain Java classes, so that anyone can work on this application, i.e., in any IDE. The point is that thanks to Maven, the app can be opened in any IDE that supports Maven, but the TopComponents have been generated in NetBeans IDE, hence they use the Matisse GUI Builder forms, which are not supported in other IDEs. It will be simple to replace those with plain Java classes, since in each case the TopComponent only contains one Swing component, i.e., either a BeanTreeView or the SHEF HTML Editor.