Pictures like background

How use the separate pictures like background for separate book?

Are you saying you want a picture in the whole background of the page with text over the top of that? More like a watermark image?
Do you have an image to give us an visual of what you mean?

Yes. You understood me correctly.

This is what I would try. I have not tried it.
Go to Styles
In the Body section doubleclick on body.story
Choose the CSS tab
Edit the following

body.story {
    margin-left: 5%;
    margin-right: 5%;
    color: TextColor;
    background-color: BackgroundColor;
    margin-top: 2px;
    margin-bottom: 60px;
}

Change it to:

body.story {
    margin-left: 5%;
    margin-right: 5%;
    color: TextColor;
    background-image: url(image.jpg);
    background-repeat: no-repeat;
    background-size: auto;
    margin-top: 2px;
    margin-bottom: 60px;
}

Insert your image into the Images Illustrations tab.

If you want one for each book then customize the style for each book.

Let us know if it works.

:crying_cat_face: No… it doesn’t work.

I don’t have time to experiment with other options like just the body.