InDesign is such a versatile program. It can not only help you format the inside of your novel, but you can create the entire wrap around cover, the front, spine AND back cover. The great part about this method is that the spine is flexible, so if your content is updated, and the page count changes, you can simply change the spine, align it up again, and export. You don’t need any higher math to complete the new size. Take a look at this video on how to set up a Book Cover with an adjustable spine in InDesign.