I have been using the Book feature since it first came out. It works great. I have used the Export to RFT because that feature does not work very cleanly.
But, what you do need to do, is to check the Page Settings for Each Chapter of the Book.
I don't change the default settings. You may, because of the A4 setting you need, but I leave the margin settings as they come with the program.
You also need to check the Header / Footer Settings for the BOOK and each Chapter.