I have a databale on index.xhtml
You've already bound the component to the bean. All you need to do is:
public void editBook() throws IOException{
int index = datatableBooks.getRowIndex(); // Actually not interesting info.
Book book = (Book) datatableBooks.getRowData(); // This is what you want.
}
The is also not needed here. For more hints also see this article.
Update: I can reproduce your problem. This is likely a bug with @ViewScoped. When the bean is set to @RequestScoped, it works as expected. Also when you remove the component binding and obtain the component from the viewroot yourself, it works as expected. I've filed issue 1658 about this.