By taking a good look at this picture, you should see how the various parts come together:
From what I can tell the BookID is a "Key" within your mod's TranslatedStringKey files. With the TranslatedStringKey editor, create a new file, put what BookID you want in the Key column, and then what book text you want in the corresponding Content column.
Then with your custom item/item template, the OnUse action would be the Book action pointing to your new Key.