Other materials
For further information about JavaFX, you can refer to the following sources.
Official documentation of JavaFX
JavaFX JavaDoc is a very good source for any extra information you want to know about the JavaFX API. It's usually accompanied with examples, and can be quite thorough.
JavaDoc can be found online: https://docs.oracle.com/javase/10/docs/api/overview-summary.html. Also, it's included in the JDK distribution and most IDEs will show it in code completion, or by a shortcut.
Besides JavaDoc, there are great reference guides to FXML and CSS in the official documentation:
The JavaFX articles set, unfortunately, hasn't been updated much since Java8, but still, it is a good source of information, https://docs.oracle.com/javase/8/javase-clienttechnologies.htm.
Stackoverflow.com
If you are not yet familiar...