Here’s another example of an image that works in both the 16:9 e-book aspect ratio and as a square for the print version of my book.
I call this 16:9, but when I measured it, I found that it’s really 16:10. I’ll expand the image in InDesign to fit into the e-book template. When expanding images it’s important to have a sufficiently high resolution that the expanded image doesn’t drop below 300 dpi. When that happens Ingramspark will reject the upload. It’s a good idea to work with 400 or 600 dpi images just in case you have to do something funky.
The e-book version of the page…
The square print version… Note the white margin on the left of the page. That margin is on the side that attaches to the spine. It’s on the left for odd numbered pages and on the right side for even numbered pages.